My dad. This is what he does: He tells you all the jokes that his friends forward to him on the internet, and then if he forgets one, he asks to borrow a laptop and starts going through his email, reading them aloud.
He's been at it all day long.
"Did I tell you the one about the dog urinating?"
"Yes, Dad, you did."
UPDATE: It's 8:55 and he's still reading jokes.