Reading Sharpstick's stories reminded me of an experience.
I was working in the Air Force in New Mexico and I was about to climb down into a rather large open top valve vault. The pipe and valve and meter were supported by the vault walls and were about 6" or 8" off the ground. Now normally we brought along a mirror on a long pole in order to check underneath these pipes, etc for snakes. And I forgot it that day. And I probably should have had someone there with me anyway.
So i climb down into the vault and sit on the pipe to work on the meter. And I feel something hit the side of my leg really hard and then start to wriggle around like crazy. I look down at my calf and see a 4' long rattler hanging onto my pants leg. We always wore lineman's boots out there because they came almost to the knee. So this rattler was evidently not happy with me waking him and bit me. But his fangs hung in the crappy nylon woven BDU pants that we wore. Now I was trying to figure a way to get him off of me, not get bitten for real and not have to kill the snake.
That was one time that I unfortunately had to kill the snake to save myself. But I didn't like doing it.