This build is for the ultimate damage/tank Amumu. On top of a good deal of health, armor, and magic resist, you have a lot of ability power that will send the other team running.

The runes for this build is what you would find on a basic tank, armor and magic resist. I added the magic pen quintessences because of Amumu's passive, despair. its always good to have magic pen on a passive that does under a 100 damage a sec.

This mastery page is probably pretty basic for a tank, making shure to go into the defencive tree and since it's Amumu, ability power and cool down reduction. I find that cool down reduction is important on Amumu because you can start a fight with his Q and end it with a Q when someone is trying to run away.

First off, I chose ignite on a tank because in a danger scenario, when you're running away and someone is chaseing you, you can stun them with Q, E directly after, and then use ignite to finish them off.(or I might be the kind of person that hates a boaster that gloats about getting away with 10 health)
I chose flash as my second summoner spell because Amumu has no running away move, and more times than not, flash can get you away from any situation.