I read a comment on a post to Security Monkey's blog that I just have to try:

It's easy to catch a fly with one's bare hands. The comments above are inaccurate. A fly jumps STRAIGHT UPWARDS before he flies off in any direction, no matter where the threat is coming from. Just clap your hands about three inches above a perched fly. No matter where he is sitting he will jump straight up into your hands and be destroyed.

It's a trick I learned at age 13 at Boy Scout Camp. Try it.

If only security bugs were that predictable.

Even more spectacular... just pass one hand very rapidly through a point three inches above the fly and grasp at the moment you pass directly above him. You'll have captured a fly with one hand, to the amazement of your fellow workers.

It works every time (after a few practice swipes.) Just don't forget to wash your hands afterwards.