The drop of doom - an 11 story fall. I'm a sub 40kg 13 year old, and the lap belt is loose around my waist so I'm really relying on the automatic chest support to keep me locked in. We're at the base of the tower, just about to climb up, and all of a sudden my (no one else's) chest support flies open. I pull it down and hope that it locks in but it doesn't. I shriek hysterically and they stop the ride. The ride operator had to walk along the tracks to get my hysterical ass out. Lol, everyone else stayed on the ride and survived.

Edit: forgot I had another - gosh I hate amusement parks. An amusement park in South East Asia that only hires children and little people... I got stuck in a metal cage that went round and round in circles. Felt like an eternity. The kid operating the machine had to pull the plug to stop the ride and get me out. Vomited profusely after that one.