My thoughts on Newnu & Willump
Tl;Dr, Nunu is Fun and for the most part a fair champion.
Nunu and Willump have finally hit live, and after playing them nonstop for a whole day in low elo, here are my thoughts.
Nunu and Willump are good at what they do. They're very good objective control junglers, and having an ability that when maxed does more damage than smite until level 18... It helps with that tremendously. Not only that, but say an enemy is on dragon early on. Snowball in when the dragon is low and if it doesn't die, you can either smite or q it. Nunu really shines against teams that have low vision, allowing him to rush in and secure objectives when needed. However, that doesn't work great if they have vision and can easily stop him.
He can build as a tank, a utility support tank, AP off-tank, or full AP. The difficult of each progresses from left to right. I find that the latter two work better for ganks, allowing you to chunk with a max size snowball. Building either of those, however, does have a drawback. If you can't get ahead early, you're useless. It's generally safer to build tank or utility tank, and easier for the objective control.
Optimal keystones are as follows. For tank, go aftershock. It allows you to get the extra damage needed for effective ganks without suffering from a lack of tanky runes from resolve. If you're going utility tank, Aftershock can still work, but guardian helps keep a teammate safer in a gank. For the last two builds, predator works great for the initial snowball hit, allowing Nunu to deal fat damage with his max snowball easier.
As far as balance goes, I'd say his kit is fairly balanced. Maybe his E can do a little too much damage if you build AP, but I feel that if you build AP and can make it that far, you deserve the damage. Other than that, I'd say Nunu is a good example of a rework done right.
Good job Riot! [slayer-pantheon-thumbs]