Funny you bring up the snakes in a hand-hold scenario. That actually happened to me while doing some top-roping at Castle Rocks in SF bay area. I went to put my hand into a nice pocket and saw something move slightly. Luckily I wasn't too tired to ignore it. When I looked, there was a small rattle snake coiled up in there.
Needless to say, I said "F@%#" and chose a different hand-hold.
