I have no tattoos or piercings, although as a kid I wanted to get my ears pierced something awful, and as a teenager I seriously contemplated having a Triforce stuck on the back of my hand.
I love the elaborate designs of tattoos, but I wouldn't want to have an overly complex one done myself. I think I could handle the needles now (but then again, maybe not...) but they look horrible as time wears on and skin stretches and/or sags. They go from being awesome to being just plain messy, like a cluster of veins knotted into something vaguely resembling an image.
As for piercings...yeah, not keen on those, to be honest. Ears are fine, but I can't help but cringe when I see people with tongue studs or nose rings. It just looks so damn uncomfortable, and I'd never have it done myself. It's your body, and you can do whatever the hell you like, but...well, rather you than me.