Don't worry, it's not as obscene as it sounds. This trick requires two
guitarists [with guitars, of course]. Be sure that you're very
comfortable with your companion, because this one gets a little personal. Both
guitarists should strap on, with the body of their guitars by their
respective pelvis areas. This requires a nice, dirty distortion of
personal preferance. Also, delay can be helpful for adding atmosphere.
Both guitarists should then rub guitar bodies together at the strings, in effect making the most hideous noise ever. Be sure to have your hands ready to mute strings for added effect. Mute at the neck to get harmonics, or the body to get pleasantly dull thumps.
I have yet to do this with my rhythm guitarist, who is not only my best friend but also female, so it would look really strange to see us having guitar-sex at a show. Have fun putting pedal effects to this.