I was at a party in college where that was exactly the game - everyone was good friends, of course - so nothing weird could happen, but the hostess had all the guys take their clothes off. The guy would stand behind a barrier with a hole at the right height (like a gloryhole). One by one the girls would walk up to the hole and reach in, and "evaluate" the cock. Not only was the goal to identify your boyfriend, but also to guess who the cock belonged to.
Surprisingly, the number of correct guesses was pretty low. If you wear a blindfold and have to pick out your bf's cock among one or two others, the odds are with you. But unless there is something extremely unique that you can pick out by feel, when there are 8 or 9 or 10 cocks for you to evaluate, it gets to be difficult. But that's what makes it fun.
Of coure, everyone out there with a wonderfully "dirty" mind can imagine other games with that "gloryhole" setup.