Shaking hands with, or other otherwise touching, an unsuspecting person directly after you have masturbated and gotten it on your hands. Cum may be rustified, or still wet.
"Dude, I so gave your mom a sticky benjamin yesterday."
"Don't worry, it was a dry one.. she had no idea. But it was hot."
A Sticky Benjamin falls into the same category as a "Dirty Sanchez," a "Rear Admiral" or a "Cleveland Steamer." Bascially, you ejaculate all over some portion of your pay-for-play partner and then take a Hundred-Dollar Bill and slap it over the ejaculate, making it stick to whatever part of the body you've spooged on. Depending upon the denomination you're using, this could also be a "Sticky Washington," a "Sticky Lincoln," a "Sticky Grant," etc.
When I was done givng that ho a facial, I finished her off with a Sticky Benjamin.