Easily Envy-kun's power to shapeshift that would just be beyond cool for me and that's the only power I would actually want..or maybe Lust-san's deadly claws as well xD both are from Fullmetal Alchemist oleh the way!
There's actually alot. One would be Shu's power from Guilty Crown (That is assuming voids and that exist.),Death the kid abilities from Soul Eater and possibly many more.
I'll like to have (From right to left) Haruhi's God like powers atau Mikuru's time traveling powers atau Nagato's alien powers atau Itsuki's ESP powers atau Kyon's! XD (I know Kyon's human, but his abilities of commenting atau controlling Haruhi are amazing!) Any of them will be awesome, mostly Nagato's and Haruhi's! X3
This is also the answer to what superpower I'd want, what wish I'd have granted, and all other pertanyaan like that. It's just too convenient and cool! Hana hana power!