self-depreciating, humorous response to the question
"What are you, a man or a mouse?"
Normally only used by men who are in fact brave, but not suicidally so.

"Where's the cheese?" may also be used or added to emphasize the response.

when you're hungover as shit after a spending a night drunk as a skunk

To Weasel yourself into a better position in poker, to gain a few measly points.