This guide goes against the norm for Rumble, which is an AP Tank. I've found that AP Tank is a massive waste of Rumble's potential. This is not to say that I would never get tank items on Rumble, just that I would focus my attention on AP instead.

The Skill Order and Item build are not a set in stone list, they are just a general setup. Look in the appropriate areas for more detail.

7/7/2011:
Flamespitter
* Damage reduced to 30/60/90/120/150 from 40/65/90/115/140
* Ability power ratio reduced to .45 from .5

This is more reason than ever to start with Electro-Harpoon at first level, since Flamespitters first level damage is so low now.

Hey guys, Warlemming here, writing my second major guide since my Veigar one several months ago. I've decided to write this Rumble guide to move people away from building the standard AP Tank Rumble, and move them towards the insanely powerful AP Caster Rumble.

The main problem people have with an non-tanky Rumble build is that he is not a very long range hero (Autoattacks and Flamethrower are melee/short ranged respectively), and that the only solution to this is to build some very bulky items to compensate.

This is unnecessary, thanks to Rumble's above average health, armour and even magic resist (one of the few heroes that has natural MR growth), plus his W, Scrap Shield, with high AP, will provide you a continuous boost in survivability.

Pros:
- Excellent AP Ratios (0.5AP/sec for 3 seconds, 0.5AP/shot (2 shots), 0.5AP and 0.25AP/sec for 5 seconds)
- High Natural Survivability
- Excellent Farming/Pushing ability
- Lots of AoE damage
- Great laning phase
- Provides High Damage during teamfights
- Spammable Movespeed Steroid and Shield
- One of the best Initiates in the game

Cons:
- Melee Autoattack Range
- Low range on Flamespitter
- Lacks Burst Damage

Firstly, I'm not going to tell you that you HAVE to use these summoner spells, this is just what I use and why.

• Exhaust: Rumble is a Damage over Time hero, so the ability to cripple your opponent and get more time to dish out all your damage makes early kills much easier and allows you to disable high priority targets during teamfights (AD Carries in particular)
  
• Flash: This ability is just too useful for escaping everything. Combined with your inbuilt shield/speed boost Scrap Shield, makes killing Rumble very difficult.

• Marks of Insight: These should be self-explanatory, MRPen runes allow you to hit harder all game, and there aren't any real alternatives for Marks.
  
• Seals of Fortitude: I take HP Base yellows for early game survivability, because my Glyphs and Quints are:
  
• Glyphs and Quints of Focus: It's hard to itemize non-mana heroes with cooldown reduction, and with Glyphs and Quints of Focus, combined with my Masteries for CDR, I have a natural 20% CDR from the start of the game. I must forgo Greater Quintessence of Health for the CDR, which is why I take the seals instead.
  
  Will go further into the high CDR later.

I take a standard caster setup of 9-0-21, since I want Intelligence and Sorcery from the lower Utility and Offensive trees respectively.

The extra movespeed, Flash Mastery and Presence of the Master from the Utility trees increase my mobility and escapability, while the Archaic Knowledge MPen from the Offense tree is a must.

• Ionian Boots: As I mentioned in my Rune section, it is hard to itemise CDR on a non-mana caster, since most CDR item's have mana related bonuses we are not interested in. With these boots, and your runes, you will have ~35% CDR very early in the game, allowing you to use your moves frequently and dominate in many areas of the game (See Gameplay below).
  
• Rabadon's Deathcap: Called the Infinity Edge of Casters, grabbing this item early in the game allows you to deal incredible damage. Even if an early Deathcap isn't possible, you absolutely must get this item.
  
• Crystal Scepter: This item is very nice all round for Rumble, providing a solid 80AP, lots of hp, and a slow effect for your Flamespitter. It also multiplicatively stacks with your other moves, allowing them to slow even more (but not by much).

• Mercury's Treads: Merc Treads are a very good choice if your enemies are loaded with CC. Unfortunately, this means giving up your Ionian boots, but sometimes you will just have to for the sake of not being rendered useless. If you need CC reduction and don't want to lose your CDR, take:
  
• Moonflair Spellblade: This will give you 25%CC reduction, and 50AP on top, which allows you to keep your Ionian boots, and get some AP on top.

• Will of the Ancients: Rumble lacks abilities that actually return health, so while he can sustain himself in battle with Scrap Shield, he will eventually be worn down and need to heal. That is, unless he has this. It's important to note that you only get 1/3rd returned health from AoE moves, such as your Flamespitter and The Equalizer, but your Electro-Harpoon will give back the full 25% spellvamp.
  
• Force of Nature: The alternate for sustainability for Rumble. This provides him with a lot of MR, and most importantly, a LOT of hp regen. Take this over a Will of the Ancients if you're up against a very AP heavy team.

• Morello's Evil Tome: This is a good choice if you decided on getting Mercury's Treads, since it will give you 20% CDR, bumping your CDR up to 40%.
  
• Void Staff: This item is almost Core, allowing you to bypass a lot of an enemies MR (49% MRPen combined with the Archaic Knowledge mastery). But there are games where every one of your enemies decides to be a glass cannon, so there will be times where this item is unnecessary.

• Zhonya's Hourglass: Gives you a lot of AP, and 50 armour, a respectable amount. The active is not to be forgotten, allowing you to potentially block dangerous Ultimates such as Requiem, Ace in the Hole and Hemoplague.
  
• Randuin's Omen: Gives you a lot of extra survivability, a nice Active, and a little bit more CDR. A good choice if you're up against a lot of AD heavy heroes.

• Abyssal Mask: A good pile of AP, 57MR, and a nice -MR Aura for your enemies. Increases your survivability while allowing you to hit harder.
  
• Banshee's Veil: Gives you more health, 50MR, and a nice passive. A good choice against a burst heavy enemy team.
  
• Force of Nature: As above, lots of sustainability, and a lot of MR.

You will need to build to suit your enemies, but a good all-round build is:


Which gives you some survivability (500HP, 50AR, 57MR), your CDR, and a LOT of magic damage (485AP+30% from Deathcap (630 AP total), +40% MRPen).

I'm going to get this out of the way first. There is a number of different ways to start Rumble's skills. This comes down to what you're trying to do, and what situation you're in. I've found that I personally prefer to go a farm heavy arrangement early on, since I'm not aiming for early kills before level 6.

However, if you want to harass your opponents a lot, you will want both your damage moves by level 2.

My alternate sequence for farming safely till level 6:

Junkyard Titan: Rumble uses a unique Heat system, which increases by 20 every time he uses a move (excluding his Ultimate). When he passes 50, he enters the Danger Zone, and his moves will deal 30% more damage (for Flamespitter and Electro-Harpoon), or shield and increase his movement by 30% more than usual (for Scrap Shield).

If Rumble hits 100 Heat, he is silenced for 6 seconds, but deals a decent amount of bonus magic damage with his autoattacks for the duration. Note, that moves that were in use when you overheated will continue (Flamespitter will keep firing, and you will be able to shoot your second harpoon).

Effective use of your heat system takes practice, but allows you to deal even more damage than you already could.

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Flamespitter: This is an incredibly good early game harassment move, with its low cooldown, allowing you to burn your enemies without drawing minion aggro. It can also be used within brush without revealing (even the flames will be invisible while in use). Note that it is not a great farming move, because it only does half damage to minions, and you do not want to be pushing your lane early game anyway with the AoE damage.

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Scrap Shield: A spammy shield, that boosts your movement speed for 1 second. Once you have this move, your early game harassment generally gets a lot more effective, being able to activate this and Flamespitter while running at your opponent, and absorbing the damage they may attempt to cause while you hurt them.

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Electro-Harpoon: Fires a slowing harpoon, and allows you to fire a second one immediately afterwards with no cost, causing a great deal of damage and slowing a target by a very large amount (especially if both shots hit the same target). Its also a good way to farm early game, allowing you to pick off creeps from a distance. The only problem is that it will hit the first minion it collides with, so you will need to move yourself around to hit some minions.

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The Equalizer: This move is simply incredible. A comparably short cooldown (especially with your high CDR), with a large amount of damage, high range, and a strong slow. It also has a unique targetting system (Vector Targetting), allowing you to deploy it in any direction from any spot in your range.

A demonstration of the damage of The Equalizer, and what not to do when hit by it.

The entire reason why one should build Rumble as an AP hero is that his AP ratios are simply Godlike

Flamespitter: Deals 0.5AP every second, or 1.5AP for a full duration burn. Already thats a very high AP ratio for such a short CD move, but while in the Danger Zone, he deals 0.65AP per second, up to 1.95AP. This is the highest AP ratio for a non-ultimate in the entire game (very close to the highest Ultimate ratios), and with it's cooldown, is ridiculous.

Scrap Shield: This move I believe is balanced. It shields for 0.4AP (0.52AP in the danger zone), for 2 seconds, with a short cooldown. It's like a half strength, half cooldown version of most other shields, but with a nice movespeed bonus thrown in.

Electro-Harpoon: 0.5AP per short (0.65AP in Danger Zone), for 1AP (1.3AP) for two sucessful shots on a target, while crippling a targets movement speed. This is again, a very strong move, with its relatively short cooldowns, and because of the slow, allows you to pull off a full duration Flamespitter with ease.

The Equalizer: 0.5AP base, and 0.25AP per second for 5 seconds, allows it to deal up to 1.75AP if someone stays in for the whole duration. While it has a lower AP ratio than Flamespitter, the amount of damage it deals in its duration is a whopping 1350 in an AoE.

Yes, this does mean that Flamespitter deals more AP damage than his Ultimate.

Overall, this means that Rumble can potentially cause in a 5 second period:
With his Ultimate: 2120 Base Damage + 5AP
Without Ultimate: 770 Base + 3.25AP

Rumble is a strong solo hero, able to lane against most solo heroes with ease (I've yet to find a hero that is consistantly problematic for Rumble). He can also duo lane well, able to harass both opponents and farm at the same time, as long as you have a good duo laning ally.

When picking your first ability ( Flamespitter or Electro-Harpoon), you will need to see what you will be laning against. If it's a ranged champion with a strong early game presence, like Caitlyn, you should take your Harpoon. If it's a hero with a weak first level, such as a melee Tanky DPS, or a caster with bad cooldowns/high mana costs, take Flamespitter and ruin their day.

Early game, you should be aiming to either harass your opponent off the lane (if possible, and it isn't always), and farming up your Ionian Boots (normally). Try to stay on your lane until level 6, at which point, either:

Go for the kill. Your level 6 strength is REALLY high, and with good use of your Ultimate as an initiate, and chasing them with Exhaust and your abilities, you will either force a Flash or successfully kill them, and can kill off the remaining creeps.

Or, wait for a new wave of creeps to arrive, and drop your Equalizer on them, wiping out all enemies creeps for the next 30 seconds.

Either way, recall straight afterwards. With the waves removed, you will be able to shop, and use your Scrap Shield without risk of your tower being pushed.

If you got your Ionians, you will notice that your Ultimate has a 60 second cooldown. USE IT EVERY TIME ITS OFF COOLDOWN (unless theres a good reason not to, like a Jungle gank being set up). This allows you to wipe out all enemy creeps, so you can push your creeps to their tower without even being there, and heavily harass your opponent, which can absolutely devastate their early game. Don't forget that each time you do this, you might be able to score a kill, sending you further ahead and them further behind.

If your opponents are not able to cause you much problem early game, farm up your Rabadon's Deathcap, at which point you should enter the mid game.

By now, you should have your boots of choice, and a solid AP item to go with it. At this point, you should start using some of your really high early game strength towards helping your other lanes (probably mid lane). Your Ultimate will allow you to initiate on your opponents every time, and due to the high slow it causes, either force a Flash or get more kills.

Don't forget to watch your towers, making sure that they aren't being pushed while everyone is away. You can get to lanes quickly with your Scrap Shield, which will have a 4 second cooldown with your CDR.

Don't be afraid to use your Ultimate just to clear a creep wave. It's got a short cooldown at first level, and an even shorter one as it gets to higher levels (down to 36 seconds with 40% CDR). It will prevent enemy champions from backdooring and make them suffer a bit in the process.

By now, everyone should be grouping up, and teamfights and ganks lurk around every corner. You want to be to reason they happen. If you see your enemies grouped up near your team, drop The Equalizer on all their heads, and make a move. It will bust all their Banshee's Veil's, and prevent them from running, allowing you tanks to get in and start CC'ing.

An example of a good initiation with The Equalizer:



This disables all Banshee's Veils on the enemy team, while still slowing them, because Banshee's only blocks the initial damage.

Don't be afraid to get in the fight. Your scrap shield will keep your health up, allowing you to deal your considerable damage with little risk.

Rumble is an insanely strong caster, who's potential is wasted trying to build him AP Tank. With some of the most ludicrous AP ratios in the game, enjoy inflicting insanely high damage to entire teams, while being able to shield damage and escape from ganks.