I've never really had any... Well, there was that one time at IB, I was on Hoosier Hurricane, and when we got to the very top of the lift, my seatbelt somehow came undone. I got REALLY freaked out because I was having a bit of trouble getting it back on, but right before we dropped I buckled it and was fine... Man, that whole ride I was thinking about where I'd end up, if I hadn't buckled it in time.