Warwick is pretty bad as a jungler. Yes he clears with ease and is safe, but pre-6 is awful, other champs can walk into his jungle and take whatever they like with very little fear of retaliation outside of the odd Q, and there's 0 fear for the enemy laners for the first 8 minutes of the game because his ganks are just so lacklustre without his ult. I can't go back to him now that I'm comfortable with Nocturne. I just feel useless whenever my Ultimate is on cooldown. Lanewick, however, is still an awful lot of fun to play.
Nunu really isn't as low tier as some players like to make out. He's still got fantastic ganks from level 2 onwards, some of the best roaming and counter jungling in the game, good scaling without farm...
From my experiences playing him I'd say his low damage output later on is his biggest problem. I'd be more inclined to play him on a team with an offensive bruiser in bot over a support (something like the support gangplank that was seen recently). I think it's mostly sour grapes and Gangplank buffs that have knocked him down on the pros' tier lists, but honestly he's still viable.
If you're just starting out, Nunu is a great character to play as with Blood Boil and Ice Blast you're difficult to gank successfully, and not dying is the second most important skill you will ever learn in League of Legends, after last hitting of course.
