Flywank

If you're looking for a good wank, get an erection and get in the bath. Fill the bath. Fill the water up to the helmet of your penis, then get a fly and pull it's wings of and put it on the end of your penis. Because the fly can no longer fly and it can't swim, it will run around in circles on the end of your penis and cause you to ejaculate.

-Ricky Gervais