Yes, it happened a few times.
Here's my favourite: I was watching tv with a friend on the sofa, and he suddenly started massaging my crotch, which made my cock hard very quickly. Without saying a word he unzipped my pants and wanked me. We had to be very silent because his friends were in the other room. He also sucked on my cock for a while but he finished the job with his hands.
Funniest thing? I didn't know he was bi!