shaco, nidalee, fiora, kassadin, and teemo seem like the 5 champs that always manage to feed horribly when they're on my team and get incredibly fed when they're on the opposing team.
kha'zix jungle is pretty strong, he's a little susceptible to being invaded since he gets pretty low doing his 2nd buff though. but he's a great duelist after first back and once he hits 6 he gets a huge spike in damage. tons of snowball potential but can also easily fall behind and has a hard time catching up due to mediocre clear times. stuff like lee sin, elise, and vi are much more reliable imo - stronger early game, more late game utility in the event that you fall behind.
been playing some nocturne recently and haven't lost a game with him yet, spell shield means he can win duels with most other junglers pre 6 and his ganks are actually decent even without the ult (really dependent on landing his q but thats a pretty wide hitbox). get doubles, gank a couple times, farm up till 6 and camp bot.
any other underrated junglers out there? i mean really underground stuff, not like wukong or gragas