Nunu is a great support early on as well as through the game. Ive used this build mainly in 3v3 matches. Nunu's Ice blast is key to a successful early gank. he works best with high dps champs like jax or yi for example. Cons are he is very squishy early game. all you have to do is be patient and not rush in. ALSO, Nunu is not a tanker, so dont act like he is. Do not try to tank a tower as he has NO attack power/speed. he's a spellcaster so treat him as such. Until high level when you can consider him a tank/mage. i suggest going top solo to farm till you have ult. Once you have ult its over. as long as you have banshee vail and time your ult right....throughout the game you will become a quick ganking machine and the WILL be scared of you :D