Troll Judge, Troll Jury, and Execu-troll.
Trundle is incredibly fun to play in the jungle. His E can block off an entire corridor to force people's flashes or combat/disengages.
Always q first, so you get the ad steal off jungle monsters (really helps with health management in the early game),then your W next. Don't be afraid to buy frozen heart early to help with mana sustain (he might be an excellent Runeglaive candidate). W increases both atk speed and movespeed, which means Trundle is powerful wherever he has time to set up shop.
He has no hard engage, but his E can definitely lock people in to a fight or otherwise scatter a team/disrupt channels. Rely on laners to set up sneaky ganks, but otherwise just join them in lane for a push to tower, bite the damn thing a few times, then walk away and resume farming and ganking.
ITEMS:
your core in the jungle is
After that, you should be building spirit visage and Warmogs (w increases healing from all sources).
That combo is all the tank you should need outside of fed carries on the enemy team.
Grab a GA, Triforce, and a Frozen Heart in whatever order you'd like, but you can swap the Triforce for BotRK or Cleaver if you'd like.
ROUTE:
start krugs, taking advantage of Trundle's fast aa speed with W and his resets on Q to stun the red buff and raptors a few times (remember to smite at end so you keep the buff longer).
Red, raptors, scuttle, wolves, blue, scuttle, grump.
Lane gank or back, then another gank, then drag.
Farm/gank until late game.
Become raid boss. Never die.