Welcome to my solotop Nunu guide. I have played a lot of Nunu and the recent buffs have made him extremely viable top. His slow, sustain, and CC all are great counters against most champions including Vladimir, Kennen, and even sometimes Yorick. His constant slow and immense sustain allow him to counter every ad bruiser in the game. His speed buff and slow have great synergy with every jungler in the game, allowing him to set up and coordinate ganks with ease. In short, he is a broken, yet overlooked champion.

I encourage you to read the entire guide, because some parts I was too lazy to separate.

Pros and cons of Solotop Nunu:
Pros
Can help your ad carry late game
Can have great ganks with other junglers thanks to his movement speed buff and slow
Has the best sustain in the game, even better than vlad's.
Has great kiting capability
Can steal buffs fast with his consume
Can even baron at 15 minutes
Is one of the SAFEST picks in game
Cons
Mana reliant until chalice
Stuns will **** on him

Let's go over his passive first:
His passive allows him to cast ANY spell of his without mana cost after every 5 auto attacks.
This means if you're low on mana, but want to get a skill out, you just need to auto attack 5 times. Timing this skill in co-ordination with your ice blast will give you great zoning power.

Consume (Q)
Nunu's sustain becomes enormous the more levels you put into it. It does true damage against minions and heals nunu for a ****ton. If you are winning your lane, max this second and max blood boil instead.

Blood Boil (w)
gives nunu attack and movement speed, and also to another ally
Share the love and buff your ad carry or teammate with this skill. When your jungler is ganking, it is amazing to use on him. It allows your jungler the extra movement speed necessary to approach your opponent or escape. This skill also allows nunu great flexibility because he can escape stick situations.

Ice blast (e)
Does a ****ton of burst early, but falls off late. This allows nunu to harass, kite, and slow enemies down for a few seconds. It's short cooldown combined with your items will allow you to spam a ton of iceblasts at an enemy, keeping them permanently cced.

Absolute Zero (r)
Nunu's ulti allows him to slow enemies in a huge aoe, and has crazy burst. The only drawback is that it is a channeled, ability. This means if they stun you, they will be able to cancel it and null most of your damage. A fully channeled nunu ulti has crazy scaling, allow him to do over 1k burst at level 11+.

You should take 9/21/0 masteries because it allows you to stay tanky while dealing damage. The 21 mastery tree in defense gives him cdr/movement speed/damage reduction, allowing you to stay bulky top against high sustain/high dps champions. The 9 masteries in the offense tree give him much needed ap and magic penetration to deal damage.

I take mpen reds and AP quints because they give your iceball huge damage early on, allowing you to chunk your opponent every time it's up.
I take armor yellows and mr blues because it gives me good early to mid game transition.

I take flash ignite because they offer the most offense compared to other summoners. I feel the damage reduction from exhaust isn't as good as the aggressiveness offered by ignite. Moreover, Nunu's iceblast does everything exhaust does, except the damage reduction. Ghost is useless because nunu has built in movement speed. Teleport is optional if you're laning against somebody likely to take TP, such as Nasus, Yorick, or Shen. Heal is bad because nunu has a built in heal. As you can see, nunu's kit gives him bits and pieces of most summoner spells, except for additional burst early on.

I got most of the item build from this blog while browsing /r/LeagueofLegends
http://mogwaismusings.wordpress.com/2012/07/31/developing-solo-top-nunu/
After playing over 100 games with solotop nunu, this build is broken.
Chalice and Glacial shroud have amazing synergy with nunu because it solves his mana problems, gives him Cooldown reduction, and defenses. This allows him to effectively counter out most bruisers top lane while being able to constantly poke with his e(snowball). If you are winning early, pick up dorans rings. They give you good mana regen, hp, and burst to help you out through early game. If you're in a farm lane, rush chalice first. If you're running against an ad bruiser, I recommend grabbing an early glacial shroud, then double dorans for burst and sustain. Towards the end of laning, if you get your chalice, shroud, and revolver core, it's best to finish off one of those 3 items or merc treads based on the situation. If they are dominating you with an ad carry, finish your heart. If you're winning, grab athenes. If your ap carry is lacking survivability finish off Wota. Towards late game, rush abyssal scepter for the amazing magic resist debuff it offers. Not only will your damage increase, but so will your teams. Finish off with Deathcap or an item like Rylais to add to your damage. If you find yourself dying a lot and getting focused, grab a guardian angel to mitigate the burst to you.
If at some point in the game you have enough money, sell your grail for a survivability item. Not dealing enough damage? Get a void staff or rylais. If you're dying too much, get zhonyas or banshees.

At level 1, try to go and take the enemy's big wraith with your consume. It will autmoatically take the wraith and give you a 1/3 level boost. If you are spawning blue, go to their top golems and take the smaller golems too. If you've done that, head to lane. If your support is willing and they aren't starting red, you may also take their red with the help of your support. Not only do you deny their red, but also can win top hard with the level advantage and slow.

Laning Phase is the best place for nunu. Spam iceballs with your passive whenever they're up and try to deny or zone them as much as possible. The more levels you get on them, the harder they will lose the lane. You can even win trades vs ad bruisers with your auto attacks thanks to blood boil. Assume their ad bruiser has 75 AD to start out with, compared to your measly 50 something. If you blood boil, you can get out more damage than they can because your slow will prevent them from auto attacking enough.

If you managed to pick up your core, try to roam mid and pick up kills for your team. It is always important to buy wards to ward the opposing team's buffs and take them if they come up. Generally speaking, if they start red or blue, the next buff will spawn around 7:30 depending on the jungler. And then around 12:30. So be aware of that and rush their buffs.

If you are coordinated enough with your jungler, you can take baron early. Buy 2 pink wards and ward top and baron to clear for buffs. Then you and your jungler will do baron. Tank baron and auto attack it while consuming at every second. This will allow you to finish it off in less than 30 seconds. It would be ideal to do this when you get your frozen heart because your armor and mana will make the baron safer.

Midgame nunu functions as an initiator thanks to his speed buff and slow. It is important that you buff your ad carry or ad jungler with blood boil and slow your target down. Then you can hopefully ultimate. It is ideal to ulti when they have blow all of their cc on somebody, hopefully you.

Late game
STAY BY YOUR AD CARRY. It is important to buff your ad carry and help him kite. The extra buffs nunu gives to an ad carry outweighs the damage output you will do to their team. If your ad carry dies before you, than that usually means theirs is alive. While you can go debuff their ad carry, it is best for you to protect yours. HOWEVER, if it is an ad carry with an escape mechanism, you might not need to babysit him, but just have the buffs on him 100% of the time.