Years ago, we were on a 727 from ATL to CAE. The plane was full, and for some reason we had a very rough takeoff roll. Just as we rotated, there was a hard bang, like what you get when you hit a pothole in the road, and that cause the oxygen mask for our row to deploy.

We touched nothing but the call button, and the flt attendant quickly put the mask back where they belonged. Still, it made for a scary moment.