This is a great way to embarrass someone that you know is always uptight and it's hard to get them to crack a smile. What you do is go up to them with a serious face and ask them the following without cracking a smile.

"Which scenerio best describes you? So you see yourself in a sword fight? Playing golf and getting a perfect hole in one? Willing to try anything once? Or are you just utterly confused by these scenerios?" Wait for them to answer, then explain each as follows: 1 Sword fight homosexual, 2 perfect hole in one heterosexual, 3 willing to try anything once "tri" sexual, and 4 confusion one confused p***s bisexual.

If they can't laugh at that, then maybe their asexual masterbates all of the time