It is really hard to say which is the best, cause there's all types to choose from, and there's many different reasons people like them.
The on I'd say I like the best in overall personality is Negi Springfield, from Negima. In conditions of power, it has to be Zaraki Kenpachi from Bleach. When it comes to intelligence, it's L from Death Note. One of my alltime favorites is Chi from Chobits.
The one chick i like the most is Kaede Nasegawa, the ninja chick from Negima. sweatdrop
Odd one, that.