L from Death Note is just brilliantly written with all his quirks and character development. Asami from Legend of Korra because she seems to have been the most level-headed and reasonable person in the series; everyone else is always angsty. Uncle from Jackie Chan Adventures -- needs no explanation.
My favourite animated character is Vegeta. I am an avid old timer dbz. There is no better moment in dbz when his future son trunks dies and he goes berserk and finally gains a respect for his son. The music from Bruce Faulconer in his transformation helps show his anger when he attacks cell for killing trunks.
Clan Defy -