Ha ha, I know right? But I can't resist. I just love the utility too much D:

AP amumu is boss. too much damage. :) I wouldn't get that Shurelyia's early though.

Thanks for the comments. Now I try and level up my tantrum first since it stays the same cost and gives me some good resistance to their basic attacks
I still get my stun first though, as always.
This isn't my build anymore, since I figured I'd win more if I stacked tanky support. Now my build is Reverie, Guardian Angel, leviathan, Abyssal scepter and Rylai's. The last two are eschewed if i need more tank.
Granted, I got way more kills this way xD

Note that you added bandage toss to lvl 3 at lvl 5 only. Anyway, bandage toss isn't needed to put that fast, if you want cooldown reduction, get a frozen heart, high armor, slow and cdr. Despite relying on AP that much, Amumu is easier played as a pure tank + cdr. Despair makes Amumu shine while Tantrum helps well early game in reducing damage. These may not seem much, but it helps alot. AP isn't needed much, but if you want, might as well get Lich Bane for the additional added damage. Deathfire Grasp also give a good 15% cdr and some mana regen, but its really useful with its active which blast 30% hp and 3.5% more for each 100 AP.
Hope it helps!

Alright. Needs a situational items section involving more Armor/MR, but it's a solid build. I'll +1.

Quick note before I read the rest of this build and forget, Bandage toss can't be level 3 when you're level 4.

Nice build, would maybe swap the Guise for a thornmail (for ultimate melee destruction), and maybe a Guardian Angel/Force of Nature to make you untouchable. Worked great for me, I loved the burst damage!