Hi for all League of Legends fans out there! I recently joined here, and I'm just DYING to let my new Master Yi build out for all of you to enjoy!
For those who haven't YET noticed who or what is Master Yi, then let me tell you. Master Yi is a great champion, capable of being one of the best junglers in the entire game. He is quite weak, and more than usually susceptible to ganks, but he will usually go down fighting, taking at least one or two of his assailants with him. So, without further ado, let us begin!

Smite. If I see any of you jungling without Smite, you'll find me in your closet when you next go to sleep... or under your bed... or anywhere large enough I can fit it. But seriously, Smite just allows you to get those buffs just before you would die. 'Nuff said.

Flash allows you to escape from deadly situations, or to follow your enemies who did the same. Flash increases your already high mobility by a little bit... and sometimes that teeny little bit is what decides everything.

Pros first:
- Yi is a very good champ to start playing, and can carry you quite high in the elos if you're good at it.
- Snowballs EXTREMELY hard(gains power increasingly with each kill)
- Yi has extreme mobility, having the highest base movement speed in the game together with Pantheon.
- Though Yi is weak to CC, he can use Alpha Strike at the correct moment to dodge it, allowing him to keep on relentlessly attacking his foe. This doesn't work on Alistar though(3 CC abilities!? Riot, seriously? XD)

And then the cons:
- Yi is quite weak in early game, and needs large amounts of farm, or a few well-placed kills in the lanes to actually snowball well.
- Yi has absolutely no CCs available, unless he has the spell Exhaust.
- If enemy team sees a Yi against them, they will ALWAYS target you first in ANY teamfight, making you their highest priority target.

For Master Yi, runes are quite important. For him I would reccomend 2 Quintessences of Attack Speed and one for attack damage. Of course, to increase his already insane attack speed, let's give him 9 Marks of Attack Speed and you've got a party going on! Then couple those with 9 Glyphs of Magic Resist and 9 Seals of Armor, and he can quite easily survive early game ganks, giving him nice early kills.
Of course someone disagrees with me on this, but as I said, this is how I play Yi, and is not meant to be a definitive or strict `guideline´ on how to build him.

The masteries I've shown give Yi radically increased damage output by the start of the game, helping in the late game. Also he gains great enhancments to his durablity by the defensive masteries. Must I say more, guys?

The items I've shown to you guys have a serious impact on whether you are effective in late game. At start ALWAYS get the Hunter's Machete and five health potions. These increase your damage to jungle monsters and allows you to keep farming for extended periods of time. Of course, this isn't a definitive guide, just my reccomendation for it.
After having the money for it, purchase the Spirit of the Lizard Elder.
- Whoa, wait a minute... the Spirit over Wriggle's? Don't you know how OP it is?
To those people I say that yes, I know how OP it is, but I want to play at least somehow fair, just like I do in Dark Souls. And the Feral Flame is just not worth it, as you need extensive farming before it takes effect, and extensive farming to actually get it to work well. I don't personally reccomend it.
By midgame you should sell the Spirit of the Lizard Elder, and should purchase Statikk Shiv ASAP. This gives you increased damage in a short window of time, increased attack speed and movement speed. 'Nuff said. Also by now you should've already started at least somehow building for Bloodthirster. Getting it allows you to have lifesteal with great damage(to add to Yi's already high damage output). Nothing else to say.
Here comes the most fun part that I like. You know how Yi has no CC? Well say again. Frozen Mallet gives Yi 40% slow per basic attack, coupled with increased health and attack damage. This is truly the item you want. It might seem nothing, but try it once, and come to me saying the same statement again with a blank face. Bet you can't.
Late Game is the time for Yi to rack up the damned critical chance. Infinity Edge increases it from 200% to 250%, and two Phantom Dancers give you total of 60% crit chance with 100% more attack speed. Infinity Edge also gives you 70AD and 25% crit chance, making the total bonuses from these three items into 85% crit chance, 250% crit damage, 100% more attack speed and 70AD. Really guys, you're kidding me.

All in all, this gives Yi CRAZY amounts of movement speed, critical chance and damage, attack speed and attack damage. This is my way on how to play Yi, and I won't enforce it to your minds unless you wish it.

This is my first build that I ever bring to the public, but I still think it went quite good. I'm also available to play with anyone who wish, EU West only. My name is Chaosking7925 there too. If we do play together, expect a graceful Master Yi gliding to your rescue whenever you need it ;)

Thank you guys a LOT for reading this, it means much to me that at least someone CONSIDERS this build.
Also, if you tried this build and liked it, don't hesitate to let it be public. And on the contrary, if you disliked this build after trying, then let it too be public. I'm always open for suggestions on bettering the builds I make, and CONSTRUCTIVE cricism is always appreciated. Again, thank you guys VERY much! :D