My hair. I used to not know what to do with it, it was a wavy floaty mess. Then I was imitating a dog once while my hair was still wet from a shower. I shook my head violently like a dog stepping out of the pond, and BAM! Curly hair everywhere. I've only had it cut once since then, which was a huge mistake. I don't let anyone convince me I have split ends anymore, they cut it all off D:
I've been growing it since 2006, it's about 2-3 feet long if uncurled. It lays about half a foot past my shoulders sometimes, and other times it curls more tightly and doesn't go past my shoulders.
I used to wish I had normal straight hair back when I couldn't get much length out of it, but after the two year mark it got so much better. Every girl I knew was jealous of my hair

I was at a prom-night alt-party once and spent the last 3 or 4 hours napping in some girls lap, whom I've never met before, just gently playing through my hair. I looked like I'd stuck my finger in a lightsocket afterwards though.
And headbanging with long curly hair flying around is very satisfying.
I normally keep it tied back lately though, just because it's easier to manage and it looked more "professional" at the job that I no longer have.