The fact that my house was broken into. It's our own fault, we left the windows wide open (they had screens in them, but, you know, still...). Some douche just wandered right in, grabbed my roommate's PS3, the cords, a controller, and two games that happened to be nearby (mine) and went right out the back door. What's more embarrassing is that I was upstairs in my room the whole time. I doubt either of us was aware of the other. We've got no real evidence(just some missing stuff and a knocked-out window screen), so there's nothing the police can really do about it. But what really pisses me off is the idea that someone is using something I paid for without my permission. I don't know if you guys have ever had anything stolen from you, but trust me...It's not a happy feeling.
It's also a bit unsettling knowing a totally random stranger just walked right into my house, but the windows are now shut and locked, so it shouldn't be a problem any longer.
Oh, and people who blindly adopt every tenant of a religion without ever questioning the source, and calling all evidence against their "beliefs" a "test of faith". I put beliefs in quotes because something is only a belief so far as it can't be proven wrong. For example, saying you believe in God is a belief because, technically, it can't be disproven. However, if it CAN be proven wrong, then it becomes a display of ignorance. An example would be believing the Earth is 6,000 years old.