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 によって the way!
I'll like to have (From right to left) Haruhi's God like powers または Mikuru's time traveling powers または Nagato's alien powers または Itsuki's ESP powers または Kyon's! XD (I know Kyon's human, but his abilities of commenting または controlling Haruhi are amazing!) Any of them will be awesome, mostly Nagato's and Haruhi's! X3