I can wiggle my ears... not totally useless, kids find it hilarious
Ah, but can you wiggle them independently of one another?
That's my useless skill.
Apparently it's borderline unbelievable to some people, too: Back when I was in third grade, I made the claim that I could wiggle my ears one at a time, and a substitute teacher accused me of lying. Needless to say, I demonstrated right then and there... but even though she was looking directly at me, literally watching my ears move, the woman insisted that I wasn't actually wiggling them.
"I don't know what you're doing," she said to me, "but you aren't moving your ears. My daughter can move her ears, and it's impossible to move one without moving the other."
The punchline came when that same teacher – intent on proving me wrong – asked me to demonstrate for the class. She had apparently thought that they'd side with her.
Suffice it to say that they didn't... and for the next week or so, people kept coming up to me with demands like "Wiggle your right ear! Okay, now the left one! Now both!"
It's really weird to me that people who can wiggle their ears can't do it independently. When I was little I figured out how to wiggle them independently in such a way that it makes my head move in a circular motion and it freaked people out.