Before any of you rag on this, I'll guarantee you that if you can land your skill shots, and use your skills with good timing, you can easily burst down any non-tank throughout the midgame. If you get fed with this build, even tanks will be decimated by your toss, cry, tantrum then attack combo. Please play this build before you comment, and hopefully you can at least tell me you had fun. ;)

Pros:

• Amumu has awesome cc, regardless of dps or tank.
• No one expects an Amumu player to come through a wall and deal 1000 mixed damage to them all at once.
• Farming is easy, especially when the mobs have -50 magic resistance.

Cons:

• The build has little actual survivability, beyond fast move speed late game.
• Amumu that doesn't build any health is actually pretty squishy. Isn't much of a con, as you should kill people before they are out of stun enough to kill you.

The runes are pretty self explanatory, as you have two stuns that deal magic damage. The attack speed allows you to get magic reduction on people and some damage right after your pull so your tantrum and ultimate do a lot more damage. I really only run armor runes because they are so nice in lane and because the physical resist stacks well with the passive on tantrum.

I'm not sure if this build will work with defensive masteries, as I'd wonder at the early game damage output. I cant see any reason to go all support, so 21-0-9 is pretty easy to justify. It is important to have as much experience as possible, as having your ultimate up as fast as possible increases your damage a lot.

This build is an item build at heart, just banking on Amumu's magic damage and magic resist reducing passive. When Amumu tosses onto someone after he has bought Malady, the few hits he lands usually gets a non-tank to -~15 magic resist, making his malady hits deal more than 20, and his tantrum do over 250 at level 5. His cry does nicely increased damage also, which ends up piling up hugely. In early game you cant spam cry, as it will make you zero your mana pool fast. Its an important skill that picks up in mob farming especially, so I then get the tome part of Nashor's Tooth. The ap helps Amumu's ability damage anyways. The late game items may puzzle some, but there is a purpose to them. When Amumu has his full build, he moves around 470 speed, which is amazing for ganking, and gives him the ability to dodge almost any skillshot. The ability/hitspam that is the tool for killing people stacks damage up nicely with the 250% hit damage from Trinity force. The build is entirely geared toward killing someone before they can do anything.

In lane, Amumu's main damage is probably his tantrum, as when he attacks people its cooldown goes down, and it does a decent aoe damage. Bandage toss is almost a must for killing, as its a high damage stun that allows you to totally close on an enemy and even get a few hits in before they are out of stun. Aside from maxing tantrum early, the other skills are almost preference. I tend to farm jungle a lot while my lane is pushed, so i get cry for for the easy quick jungle. it also adds nice damage to those affected by malady and Amumu's passive.

Summoner spells are probably what can change the most based on preference with this build.

I get ignite so i can get easy first bloods on squishy solos. Masteries are set up so that the cd of ignite gives ap which adds damage.

If you go without Ignite, just remember to change the mastery to something else.

Flash is a summoner spell that is just too good to pass up for most of my builds, as it is such good utility in general. Easy to flash when you barely miss a kill, or they flash right before you wanted to ult, or you need to run through a wall without a mob to toss to. Flash is almost always extremely useful.

I can easily see the use of exhaust to increase killing output, but most other summoner spells aren't going to help you kill anyone. If you need movement because its what you are used to, or you need heal because sometimes you overextend a little, then do it.

This is a bit of a trial guide, to see what people think. If there are any questions or criticism, lemme have it.