Always bear in mind, whatever funny thing you can do, someone else can probably do it too. I mean, I can make my eyes shudder, which freaks some people out, but it's funnier when they do it back.
I can't touch my toes, can't do press ups and my fingers barely bend past 100 degrees, but I think that's just lack of use. That reminds me, try this, folks. Make circles with your thumb and index finger, then put the knuckles of your index finger (still with thumb) under your eyes. Tilt up until it looks like you're wearing goggles. Everyone in my family except my dad can do this, and we mock him.
I can turn my tongue on it's right side, which is embarrassing if everyone else in the room can do it. Especially if someone who can't then turns up and we're all doing that.
I seldom get tired. I can wake up at godawful in the morning and be absolutely fine. Just don't try and talk to me, okay?
My knees crack whenever I bend them, and everyone looks horrified.
My good friend is a basket case for things like this. He can move his kneecap about (ever since he ripped it halfway up his calf), he has a sleight of hand matched by no one, can circularly breathe and his hand goes red in cold temperatures and never gets cold. There're a bunch more things I can't remember, but hey.
Oh, and if your eyes are different colours, it's called heterochromata (sounds so much cooler, no?).