If there's one thing that makes me throw up...

If there's one thing that makes me throw up, it's a dart board on a ceiling.

This is a pun. The pun is centered around the words "throw up". Throw up usually means vomit, or chunder, however in this instance it means throw darts straight upward into the air. The listener assumes the normal definition of throw up when they hear the set up of the joke, but the end of the makes it more likely it is the alternate definition, and that confusion that it causes is funny.