Hi,
my Nickname is Forged09. I have played about 700 games, i know that are not much, but i must show this Guide at Mobafire.com.
My Build for Amumu is not for a lane Amumu, but for a jungler Amumu which is a hard tank at any time in the game.

I have:
9x Greater Glyph of Shielding(+0.15 magic resist per level(2.7 at level 18)

9x Greater Seal of Shielding(+0.1 magic resist per level(1.8 at level 18)

9x Greater Mark of Warding(+0.97 magic resist)

3x Greater Quint of Resilience(+4.26 armor).

My Masteries are 0-30-0. Technical i do not want to deal damage, i play Amumu to stun champions and safe my ally champions.
This Masteries i need to be a strong tank.

I start my build with 1# Regrowth Pendant and 2# 1x Health Potion, to regenerate my life constantly in the jungle.
3# are Boots of Speed and 4# Philosopher's Stone, to be faster in jungle and get mana and life much faster.
5# Chain Vest then 6# Giant's Belt
7# Mercury's Treads, for better ganking and magic resists.
8# Sunfire Cape, for more splash damage.
9# Frozen Heart, 10# Force of Nature, 11# Warmog's Armor and 12# Abyssal Scepter are for my tanky build.

First i level up Despair, to deal more damage in jungle and on champions.
Tantrum at level 2, is very important in jungle.
I level Bandage Toss at level 4 to gank better.
After i level up Despair, i level up Tantrum and then Bandage Toss.

Really easy,
smite is for jungling.
Flash i take to gank better, for example to come in range for ulti to stun
or i use flash to survive.

I start at blue. The blue must pulled and then it easy to kill the blue with Despair and smite.


Order: primary route: blue->wolves->wraiths->golems->red
secondary route: wraiths->wolves->golems

Jungle till you can buy Boots of Speed and Philosopher's Stone.

Then go gank.

If you have LOL Recorder search for "Forged09 Amumu Jungle Route", there you can see it, how it works.

Pros: good ganker
nice in teamfights
hard tank and damage dealer
really fast jungler

Cons:-

early game: -you make much damage, but they can catch you easly
mid game: -more balanced: smaller damage, hold out more
late game: -when you are maxed out: -you are unkillable
-the build shows their effectively
-your life regeneration is high
-you can stay in fights very long
-you deal so much damage

You are the tank.
Stay in front of your team, you should defend they.

team fights: -to start a team fight, use Bandage Toss to get in the enemy team
-activate Despair and spray Tantrum
-when you have many summoner in the range for ultimate you can, activate it
-then focus the damage dealer in the enemy team and kill him
=TEAMFIGHT WIN