Tier 1 - Udyr, Trundle, Skarner, Lee Sin, Nocturne, Fiddlesticks, Nunu, Cho Gath
Tier 2 - Shaco, Riven, Jarvan, Amumu, Gangplank, Maokai, Rammus, Shyvana
Tier 3 - Xin Zhao, Fizz, Malphite, Master Yi, Olaf, Warwick, Tryndamere, Yorick, Gragas
Tier 4 - Alistar, Blitzcrank, Akali, Sion, Graves, Galio, Irelia, Kayle, Renekton, Nasus
Tier 5 - Karma, Mordekaiser, Pantheon, Taric, Wukong, Jax, Evelynn, Talon, Orianna
Fiddlesticks is one of the best junglers in the game.
Pros
The only true AP jungler.
Has a huge impact on a teamfight with a well placed ultimate.
Terrify is one of the most ridiculous CC effects in.
Two types of CC (Silence/Fear).
Cons
Extremely squishy.
Early ganks aren’t that great since you only have drain or a short fear.
Easy to be focused or killed when ganking.
Everyone hates you because of your fear duration.
Source: http://www.mobafire.com/league-of-legends/build/who-is-your-jungler-and-what-does-he-do-114118