I stole some beers at a party once. A friend and I weren't feeling the vibe, took a few bottles and went somewhere else. I feel bad about it, he was a good dude and didn't deserve that.
I got trashed at my 23rd birthday party a friend threw at her house. It was mostly people she knew, but as I was passed out someone stole my wallet.
My brother stole quite a bit from me during the height of his addiction. He's been clean for several years now though. I'm glad I've got him back.
Oh, and in elementary school when they were at the height of their popularity I had one of my holographic Charizards stolen. Dunno who took it, someone had a come up.