Trundle is one of the best if not the best juggernaut pick in the top lane if played by an andequate player. The king of teamfights and 1v1s, a super tanky troll with built-in healing and all kinds of debuffs which help him to plough through his enemies, also works great as a support with certain AD carries. He also counters every tank/juggernaut in the game, since both his Q and ultimate steal his enemies' stats. Contrary to his appearances, this champion is great at teamfighting, and best at frontlining and catching enemies. It is not worth to play him the way you would play as Yorick, you don't need to build hullbreaker either because both your push and 1v1 is strongest in the game.

There are quite a few Trundle tricks that not many people know about.
1. Auto + Q animation cancel
This is the bread and butter trick if you want to be an effective top laner. Lets you win trades fairly easy. During the end of your auto attack animation, hit Q and deal more damage in faster time. It's great at cheesing, and even better at finish off your targets. When they are low, flash for them with auto attack, and Q immediately after, they will probably flash away, but your Q is going to kill them anyway.
2. Proper W usage
Way too many people in low elo forget how helpful this ability is. Whenever you're about to receive any healing, remember to use your W before. e.g when your team is finishing the baron, use your w to heal back to full health. Same goes for all the dragons and big monsters in the game. Try not to forget to use W before ulting, it will make you unkillable in a 1vs1.
3. The R kill
Sometimes it's better to bait your opponent out and finish them off with your ultimate - it deals quite the damage if they are low health, and it's also a DOT ability, meaning that if they leave with 50 hp after the first cast, the ult is still going to get them. If someone's low on health you can always flash + R to finish off your target from a ranged distance. Most people don't expect this.
4. The proper pillar placement
Trundle's E is what makes him a not so simple juggernaut. Its correct usage requires a lot of skill and good timing from a player, and if used properly - it is able to turn the entire fight on your team's side. E.g. Blocking lee sin's second Q, Zac's E(very simple), even Jax's Q and Xin Zhao's E or Malphite's ult. Basically any dash with cast time. It also works good against hooks. You can save your allies from Blitzcrank's hooks with using the pillar on your ally just when he casts his Q. To counter Nautilus, simply put a pillar in front of his hook so it doesn't connect to your teammate. Even if you are able to pull those tricks off, it's still a russian roulette - you never know what your enemy's going to do, but practise and you'll be able to shine as a player with some real skill. Another thing with pillar is cutting people off - use it near walls so your enemies will have to go around - leaving them as a prey for your ADC or an assassin. If you're lucky enough, you can even trap people between pillar and the wall. It's not the easiest thing to do, but if you manage to do so, it will leave them without any way to escape, and force to use flash or simply die. A well placed pillar in late game is a death sentence. A 60% slow is almost as high as Nasus's W, but it is an AoE ability, and you don't have to be that great at aiming.
These are all the major tricks you can learn to perfect your playstyle as The Troll King.

I started to really main Trundle at the start of S9, when he received some buffs which made him a champion again, not a cannon minion that he used to since may 2018 after some enormous nerfs. Playing him top brought the most fun, so I started learning the champion and actually managed to win 95% of my lanes. After hitting P4 with the troll, I realised that I was marked as one of the best Trundle top player in the world, with about 80% win rate in over 100 matches. I managed to hit P1 just with him, but had to stop because of my back surgery, which made me abandon the game for the next 4 months. I hit P1 and on June 25, 2019 I also hit rank 2 global as Trundle top. I haven't got any screens except the one where I am rank 3. Now I'm trying to get back to game, I still win easily, but after those tiamat changes, Trundle was hit really hard. Tiamat made you win and stomp the lane, helped with combos, and ravenous/titanic hydra reset was the best thing ever. I truly miss those times.