Two completely separate incidents, both terrible.
1: I was in the studio with a 10D and a 200mm f/1.8L (this was around 2004 so the 10D was still hot stuff!). The worst possible thing that could have happened, did happen. The tripod head was not as tight as I thought it was (given that the lens was quite heavy, it MAY have pulled it loose, I'm not sure. At any rate, during this tipping over incident the sheer weight of the lens caused the tripod plate to ALSO come loose! The whole thing came crashing to the cement studio floor!!!
When I picked it up, I was prepared to kill myself, but all appeared to be well! The lens was a rental from school and when I turned it in I told them what happened, they said "oh don't worry, it happens a lot, thanks for being honest"
Turns out the only damage that happened was to my 10D, I broke the pop-up flash. That's what hit the ground first, glad that's all that broke!
Situation 2: I was doing a model shoot down at the beach, I was shooting with my Mamiya RZ67, I decided to be dangerous and actually get in the water for a closeup shot. While focusing, a larger than normal (for the current tide) wave came right up and SOAKED my camera. Thankfully again I was spared and nothing was ruined, even the film was OK! I'm convinced that camera could survive a nuclear blast.
So those are probably my two worst accidents so far. Hopefully I don't have anymore!