my vote goes for shyvana. She has a really fast clear speed, is really safe, does a lot of damage and becomes absurdly tanky with few items. Her main problem is that her ganking sucks. Though you can take exhaust to sort of remedy that.
Lee sin is a total boss too. One of my favorite junglers, but I don't often play him due to his rather lack luster late game. If you're fed out the ass or something, you'll destroy people, but I find that his late game is rather boring and somewhat useless. He is very strong in the early game though.
I would also try jarvan next week too. He is more of a tank jungler and you won't really be building aggressive on him, but he has very good ganks, and his ult is amazing. Though it has a lot of potential to screw your team over too.