I can only think of two really. 1. Please don't kill me (or do something bad to me). 2. Stop telling me your nonsense - I don't want to hear your lies, excuses, etc.

Stop talking. Show mercy. Save effort. Give me something. Sarcasm. Prevent harm.

Besides what Claire said, I have also heard this used in "Spare me the details" meaning "Go to the point" or if someone is telling you something disgusting you don't want to know about, or a part of a story you are not really interested in.