My favorite is the Chesty Puller quote already posted.
Couple years ago I found the Gerber boot knife I carried in the Marines, it was in the back of a drawer in the dresser next to the bed. Wife was walking by and I said: "Look what I found!", and immediately fumbled it as I held it up to show her. It was still very sharp and landed point first in my thigh. Stuck there almost an inch deep. She could hardly patch me up because of laughter and still reminds me of it often.