You have enemies? Good, that means you stood up for something.
Already been said, but I always have the same answer whenever any question of this sort comes up. Anything involving time control, even if it's just to stop it. (Although traveling through it would be cool too).
It just has the most real-world uses, and would be the easiest to conceal. Not to mention it's fairly strong in terms of fighting as well, even something with Superman level strength can't really do much when they're stuck in place because time is frozen.