An acronym meaning "Read the Holy Bible." Useful in conversations with Christians who have somehow missed out on rather significant parts of the book, ignoring verses that don't quite fit their worldview.
It also has the advantage of being similar to RTFM without the obscenity.
Skeptic - "Jesus commanded his followers to obey the laws of Moses. Salvation through faith alone isn't a Gospel doctrine."
Christian - "What? Show me the verse, and I'll believe you."