A Few Suggestions

I was carrying groceries in the other day, climbing the stairs because the elevator STILL isn't fixed yet, and I realized that two hands is sometimes not enough to get the job done. I thought it would be pretty useful to have either another set of arms - four total - or a prehensile tail. I couldn't decide between the two, because two more arms would be really handy in a fight, but with a prehensile tail I could hang from things like a monkey. Or a possum, whatever.
   That got me thinking about what I would do to improve the function of the human body. It's great the way it is, but, really, it could stand an upgrade.

Another opposable thumb on each hand. This would make sure you didn't drop a hammer onto your toe, for instance, and would make for some really interesting musical instruments.

Removable skin. I know, it sloughs off and renews itself now, but every so often don't you just want to tear it off and start over again?

Directional ears, like a cat's. When commercials on the TV are too loud and you can't find the remote, you could just flip your ears back and reduce the volume.

Elbows that could bend the other way. Right now our elbows are limited to less than 180 degrees of movement. Think of the torque you could get on a baseball if your elbows bent down a few more degrees.

Eyes that can see in the dark. Think about it, no more stumbling over shoes and clothes on your way to the bathroom in the middle of the night. You'd need another eyelid or something to make it dark enough to sleep.

Half your brain turns off at a time. Like dolphins, who let half their brains sleep while the other half keeps on going. Think of what you could get done if you were mostly awake all the time. Of course this would be bad for the mattress companies.