
Rubbing a cock between well oiled butt cheeks can be a nice alternative for times when anal sex isn't on the table for whatever reason. I imagine it could also be a fun way to tease the other partner before the main act.
Intercrural, rubbing the penis between a partner's thighs, used to be another popular non-penetrative alternative to anal, especially in ancient Greece.
There's probably no question that most members of this forum would prefer the "real deal", but I'm still curious how many of you enjoy these activities.