Well, considering the fact I am male, and as such hold rather a lot of interest in females, Invisibility would be an obvious choice for reasons that need not be specified, hur hur hur.
Alternatively, quick save/quick load would be amazing. Just to redo a part of your life instantly; basically going back in time.
But...if the choice is made based on if I ever found myself in a situation similar to that of a main videogame character (i.e. mortal peril), I would have to go with the army skills of XIII. Anyone played that? The cell-animated thing with the amnesia plot-line and cartoon-like "kaboooom!"s when you blow stuff up. To be able to visualise where people are round corners by listening/seeing the tap of their feet, quick heal, lockpick in 2 seconds, etc, like the character does would be ultra-cool.