This is my first guide and I'll be demonstrating my playstyle with Nunu.

Early Game
I like to be in the opponents faces and then quickly run away before they have time to react. Start with Doran's Ring and combo your passive to make sure your mana is always high. you don't want to be sitting on low mana when your opponent overextends and you're all like.. well ****. not enough mana to cast my ulti :/

First point goes to ice blast because with your magic pen runes and your ap qlyphs+quints you're going to hit like a truck. This is your bread and butter early game. Abuse it along with your awesome passive. It has epic slow capability so you can easily catch up and finish the opponent off with your laning partner for first blood. (you can't do this if your partner is a squishy carry)

Next point in Consume. This means you will never have to recall. NEVER. unless buying items...

At level 4 you will get your blood boil. Do NOT be afraid to use this. Chances are if you're laning with a carry they wont much atk speed at lv 4 so this helps them out greatly. At low mana you dont even need to wait for your passive to cast this.

At this point you're getting close to 1k gold. Quickly recall and buy boots of mobility. Yes. I know most people buy Sorcerers boots but the way I play Nunu I dont want high AP output end game so i have no need for sorc boots. By the way did you know that when you have boots of mobility+ghost+bloodboil you're going to go ****ing fast. Very good for saving a dying tower or helping a team mate out by rushing in and slowing.

Next rush your Rod of ages. Good survivability+AP damage output... **** yeahz.
get your catalyst first as it will help restore mana and health if you are lacking it... which you shouldn't. If you're feeling confident get blasting wand first.

At this point you should be 1 or 2 levels higher than everyone else other than the solo midders. Your consume should have kept you in lane well enough to not recall too often. Hopefully at this point you should be 2/0 3/0 or 3/1. Nunu's ultimate has such high damage output early game that kills are almost always ensured.

Mid Game:
You've entered the mid game. You're hitting people really hard with your iceball. You want some more AP. Make people fear you. next Build your zhonya's Hourglass.
By this point the enemy will have caught onto how high your damage output is. They will almost certainly try and cc you down so you can't cast your ulti. This is where zhonyas comes in. Instead of going for banshees and stopping 1 attack. You're going to get this and try and make the enemy "forget" about you. Flash into the middle of the enemy team and pop your zhonya. They'll be like wtf? why can i not target him? oh well might as well kill some other people. Bam. Activate ulti as soon as you come out of zhonya active.

Late Game:
K now they're pissed. They're all trying to aim you and try and stop your ulti. Build you banshees now because you need the extra health+magic resist when they're focusing you. After that you want Gaurdians Angel for more armor and more Magic resist plus its sweet ability.

In late game you are no longer the nuker. You're not quite the tank either. You're more of a tankish-support-distraction-slower. yeah... hard to categorise. You want to try and channel your ulti as long as possible after ending zhonyas and then soak up as much damage as possible WITHOUT DYING. wow i want to stress that alot. YOU ARE NOT THE PROPER TANK YOU'RE NOT SUPPOSED TO DIE. banshees will hopefully help you if you're not out of the fight already but even if that fails you still have your Guardians Angel ready. As soon as you come out of Guardians Angel pop ghost and bloodboil.. gtfo buttons ftw! Hopefully they'll be so intent on getting revenge on you that they wont notice the farmed AD carry ripping thier team to shreds in time. Last Item can either be Thorn mil or Force of nature.

To prove this works I'll recount a game i played just 2 hours ago. I flashed in and didn't have time to pop zhonya's hourglass.. oops. they mowed me down instantly. Lucky for my Guardians huh? You bet. While they were all sitting around like ******s my friendly mordekaiser AP nuked them big time bringing them all down to roughly half. I got out of G.A. and they all pounced on me. BAM zhonya's **********er. Once it ended i activated ghost and ran. they all followed of course oblivious to the Mordekaiser just owning them from the back. I got away... on 10 HP. Maybe luck but as i was running the rest of the team, carried by mordekaiser killed them all. Aced them. Our teemo didn't lose any health. niether did our xin xhao.

That game i got 14/3/13. Everyone else in the game including enemies had almost triple my number of deaths.

I should've got so many more assists but being a distraction and piss bolting doesn't give you any unfortunately. But you know what was cool about that game? We won. And when you get down to it the number of kills or assists or towers you get are irrelevant. the better team is the one that pushes, works and co-ordinates efficiently.

gg