The ability to "hear" bat echolocation nearby. I use to be able to do that. It wasn't so much that I heard them, it's that when they were around doing their thing, everything I did hear sounded funny. Lost that ability around the age of 15 or so.
I can hear bats. And dog whistles. And those "ultrasonic" sirens that are supposed to stop cats crapping on your lawn, MAN are they annoying, and they're NOT ultrasonic 'coz I can hear them >.< Kids can hear higher sounds than adults, guess my ears never matured.
Anyway, useless superpower :-
Being able to hover like a millionth of a millimetre above the ground.