LORE

The Freljord is an unforgiving place, a mountainous land covered in snow and ice. Travel, especially in the winter, can be very dangerous. The elements often claim even those who have spent their entire lives there. The boy known as Nunu is one of those who fell prey to such tragedy. One day when he was a young child, Nunu rode on his father's back as they returned from a trapping expedition in the mountains. An unexpected blizzard came upon them, forcing them to seek refuge in a cave. The tempest lasted for days. Nunu's father had to leave to find food, but never returned. Eventually the blizzard cleared and the young child lay dying on the mountainside. Fortunately, this was the land of the yetis, powerful beasts with whom Nunu's father had secured an arrangement for safe passage. A young yeti boy named Willump found Nunu and brought him home. From then on, Nunu was raised by the yetis. When the League of Legends was formed, the yetis knew they needed a champion. Riding his brother Willump, Nunu became that champion.

''Imagine what Nunu will be like when he grows up!''

Stats

Damage 51.06 (+3.45 / per level)
Health 437 (+108 / per level)
Mana 213 (+42 / per level)
Move Speed 315
Armor 16.5 (+3.5 / per level)
Spell Block 30 (+0 / per level)
Health Regen 1.41 (+0.16 / per level)
Mana Regen 1.32 (+0.1 / per level)

Pros

Easy to learn
Cheap to buy (450IP)
Self heal
Free spell after every 7th attack
Amazing AP ratio on skills (resulting in lots of dmg)
Great survivability
Can handle a 2vs1 lane with ease
Great symbioses with carries

Cons

Often target of CC
Ulti can be stopped with Stuns, Knockbacks, etc.

Quintessence: Health for more survivability early game
Marks: More damage for your Ice Blast
Seals: Mana regen to be able to spam Ice Blast constantly from the start
Glyphs: CDR to spam your skills more often

Offensive Tree

15% Magic Penetration to achieve more harrasment early game along with extra AP to get minor damage boost. CDR also works great on Nunu as his Consume has a pretty long CD

Defensive Tree

Nunu is tanky by nature and we just want to emphasize that. Along with these masteries Nunu is tanky enough to survive almost every burst and every teamfight long enough.

Utility Tree

The only reason why you want to get this if you need mana management. Nunu has a free spell every 7th attack with Visionary. No need for these masteries.

This spell is great for popping up Absolute Zero in the middle. Just flash in after the initianol round of stuns and see how your ultimate get's a good channel and makes everyone run away. It's also great for jumping over walls, getting away from ganks (this is the most important as Nunu is very prone to ganks), tower diving (dive someone who is low and Ice Blast them).



Nunu wants to be fed at the start so he can build his Rod of Ages as soon as possible.
Along with flash this makes you a very powerfull tower diver. It also gets rid of those pesky luckers who made it to there fountain with less then 50 health.


Plausible Summoner Spells:

Cleanse
You will be the target of many CC because your insane ultimate. Use this if you think you need it.
Ghost
Many people prefer ghost over flash. The only problem with ghost is that it does not bring you to the middle of the battle instantly to pop your ultimate. If you like extra movement speed just use Bloodboil.
Teleport
Always a good spell cover large area's and help out without having to walk.
Exhaust
Gives Nunu an extra slow. Ice Blast --> Exhaust --> Ice Blast and a chase won't last long.

2vs2 Laning

Early Game (lvl 1-9)
Start out with Sapphire Crystal, Health Potion and a Mana Potion. We need the extra mana because we will be spamming our Ice Blast at the enemies whenever possible. Pots are to cover up a big burst you took and possible mana problems. Remember to stay agressive! Consume will heal you more then enough to stay hitting minions. Hit minions whenever possible to get a free spell and use it directly! This way we can start charging a new free spell and we don't waste our awesome passive. Try to target Ice Blast at the most squishy champion your laning against. Once there half dead and your laning partner has a stun, knockup or anything like that you should go after them. Let them push a little so there is still enough room to chase them for little while. Let your partner hit him with a stun and directly as they come out of it you should use Ice Blast. Keep auto-attacking them and Ice Blast whenever possible. If there not dead by now you can Flash --> Ice Blast --> Ignite them to garantuee the kill.
Keep doing this till you can buy at least Boots and have half the gold required for Rod of Ages. You should be able to get this at the 15 min mark if you are agressive enough. Try to use Consume on every big turret minion to get the most out of the spell.

Mid Game (lvl 10-14)
Your laning partner can help out other lanes as Nunu can easily maintain a 2vs1 lane. Play defensive and don't try to be a hero by getting a kill. You will most likely die and your team loses experience in that lane. Keep harrassing them with Ice Blast, healing with Consume and just be annoying as hell. In case another lane needs help you can go there and help them out, but it's best to stay in lane as long as you can. Eventually they leave your lane alone and you can push a tower by yourself, but remember to watch the ganks (wards a very helpfull).

Late Game (lvl 15+)
You are more often needed in team fights and should have a big boost over the enemies because you are at least 2 or 3 lvls higher then they are. In team fights try to constantly use Bloodboil on your carry as it will increase his damage output significantly. Even use it when both teams are waiting to initiate! The spell has a lower CD then it lasts so you can keep it up all the time. After the initianol round of stuns have happened you can flash in and use Absolute Zero. They can't stun you if you go in in at the correct moment and thus you can complete your full channel. While they are probably running away out of it's zone your team can kill them without any backfire. Remember you can release your ultimate prematurely to get a smaller % of the damage! Don't let them run out and not get any damage!


2vs1 Laning

Nunu can also take the 2vs1 in case you have a jungler on your team. Just play under your turret, but stand in front of it. Nunu can easily handle the little damage minions deal with Consume. Keep harassing the squishier champion and ask for a gank whenever the jungler is ready. Your laning enemies should be overpushing all the time and making a gank pretty easy. Further it's almost identicall to 2vs2 laning. In case you have a hard lane you might want to get Catalyst the Protector earlier to get some extra heal each time you level up.

Core Build

Mercury's Treads
Anti CC boots. Nunu will often be the target of CC because of his ultimate.
Rod of Ages
What more do you need? A good AP, health and mana boost, everything that a good Nunu needs.
Banshee's Veil
Nunu hates it when his ultimate gets interupted by a stun. This gives you a clear advantage as the enemies will have to use another spell to interupt your ultimate. This also helps Nunu to become the tank we need him to be late game.
Gaurdian Angel
If you are often the target of CC you will also be the target of bursts that follow. This can resolve in a quick dead if your not paying attention. What is more hatefull to revive unnoticed in a teamfight and pop your ultimate straight up?

*Update 21 april 2011*
My friend, yog soggoth, pointed out that the usage of Hearth of Gold could be very usefull to get early game against a high AD team. You can later build it into Randuim's Oomen.

*Update 14 may 2011*
New Tendacy Items. It can be helpfull to get a Eleisa's Miracle and switch Mercury Treads for Ninja Tabs. Suggested against a high AD team

I left 2 item spaces open. That's because every game is unique in it's way and thus we must alter our gameplay along with it to achieve the most out of it and finally getting the win.

Against Magic Damage:
Force of Nature
Great for a bulky Nunu. The health regen is absurd as nunu easily achieves 4k health.
Quicksilver Sash
It's the only thing that removes debuffs such as Mordekaiser's or Vladimir's Ultimate. Also works against Malzahar's and Warwick's Ultimate. I also consider this as the cheap version of Banshee's

Against Physical Damage:
Sunfire Aegis
Gives you armor, health and a nice Unique Passive.
Thornmail
Great against squishy carries, let them kill theirselfs by letting them attack you.
Frozen Hearth
Perfect against melee carries like Xin and Yi. Also gives you some CDR to get a very low CD on Ice Blast


Semi Defensive/Offensive Items
Abyssal Mask
Great synch with your ultimate and some MR along.
Rylai's Crystal Scepter
Health and more AP, too bad the slow doesn't stack with Ice Blast. *Update* It does stack, but the amount of extra slow is only 10 movementspeed at best *Update*

Always good to get
Aegis of the Legion
Gives you everything you need against a very balanced team.
Warmog's Armor
More health! But without any armor or magic resistance it's useless

Wait for the initial round of stuns in teamfights before setting up Absolute Zero to get the most out of it. This does not mean you have to wait outside of the battle though.

Try to fight with enemy minions against another champion. During the fight you can use them to heal yourself with Consume and changing the outcome of the battle.

Use Bloodboil on another ally to get 2 buffs, one for the ally cast on and yourself. Try to find an allied champion, if there not around use it on minions.

You can easily kill a melee champion that is slower then you by kiting him and using Ice Blast correctly. Try to maintain his aggro but don't let him come close enough to attack you. 1 on 1 this is a very powerfull tool.

If you see the opponent has a champion with Smite in the loading screen you take Consume at lvl 1. Next thing you do is rush over to the 2 golems and steal one. This will slow them down a lot. If you really want to be bold you should consume the blue wraith and then go to the golems.

When your trying to take down a turret with your team you can zone enemies out with Absolute Zero. You do this by running ahead of the tower and using your ultimate as soon as you see enemies coming over. They will think twice before running in your ultimate and it gives your team a whole 3 sec more to take the tower down, which is often more then enough.

I hope this guide is helpfull for the Nunu players in LoL.
If you downvote please let me know why.

Updated:
12-5-2011: Added a few tips & tricks
14-5-2011: Added another tips & tricks + New Tendacy Items Suggestion
5-6-2011: Edited Rylais Scepter
3-8-2011: Updated some minor things