Lee Sin is one of the strongest, if not the strongest jungler in the game right now. His counter jungling prowess, skirmish strength, mobility, and great ult give him all the tools a jungler needs to dominate a game. He is however one of the hardest junglers to play, given that he has six spells and so many small interactions, combined with a skillshot Q and one of the hardest ults to use in the game.

Pros

Insane mobility

Very strong counterjungling

Great ganks, particularly at level 6

Extremely strong skirmish potential

Cons

hard to play

Weak CC

Must build tanky to be effective in high level play

Recovers poorly if behind