Birdy

Cowboy Bebop

Dragonball

Flame of Recca

Gundam Wing

Hunter x Hunter

Inuyasha

Mononoke Hime

Oddments

Outlaw Star

Ranma 1/2

Rurouni Kenshin

Trigun

Yuu Yuu Hakusho

Muahaha
It's rare that you can grab a cel of an anime character actually saying "Muahaha" but this is pretty close!
 
Added: 7/4/05 From: Celga
 
Muahaha