Hello.This is a guide for players who like to play Nunu as tank.I make this guide with lots of health and i hope u enjoy playing Nunu :)

I personally chose some ability power as you will need some and i also chose some health regeneration runes to survive more in the battlefield.Some magic penetration will help nunu when using his Absolute Zero and his Ice Blast

Offence is a good choice for nunu because it gives all of Nunu needs like magic penetration attack damage,speed and other bonuses that will definitly help Nunu throw the entire game.After you have completed the offence talents you should put some at utility reducing the time spent dead and giving you some bonuses in health and mana regeneration.

MERCURY'S THREADS is a good item to start with as it gives you some speed and some bonuses that allows you to escape from enemies that are chasing you.
SHURELYA'S REVERIE it's the second item that will help you.Because of it's health and it's big health regeneration.It has a lot of bonuses who will make a difference between dying and escaping.
MORELO'S EVIL TOME is also a good item that will help you with some ability power,mana regeneratioon and also ability cooldown which i think it's important for Nunu.
RANDUIN'S OMEN it's a must have item for Nunu as it will help you with the health,some good armour,big health regeneration and some nice passives it has.
ROD OF AGES is also a very good item as you will get lots of health and mana from this item,also you will get some ability power.
SUNFIRE'S CAPE is the last item and with it's 450 health,45 it's armour and it's passive your chance in survivality will greatly increase.

When starting a battle i first recomend using it's ICE BLAST as it deals damage and it slows the target's movement speed being easier to chase the enemy.
Then it's good to use the BLOOD BOIL to deal some damage and make sure he can't escape very easy from you.
Don't forget.If you run out of life in battle it's very usefull to use Nunu's CONSUME to deal a large amount of damage and heal you for lots of health(WARNING:you can use CONSUME only on minions(creepies) or from the creatures in the jungle)
If you see your enemy is doing well you have to use ABSOLUTE ZERO to deal a very big amount of damage so you can make sure you can kill him easier.ABSOLU ZERO it's useful while attacking enemies that don't have big health because you have chances to kill them with your ultimate

EXAUST is a very good spell for Nunu as it reduces your enemy's movement speed ,attack damage and other.With this spell you can kill other champions easier.
FLASH it's another spell that is useful for Nunu because you can chase enemies and you can escape from ganks or ambush

I hope you enjoyed this guide for Nunu tank.I will sometimes make updates at this guide.Don't forget to vote and comment please :)