Very popular cruise bar at the SoMa neighbourhood. It has a small semi-outdoor smoking area that turns into a sex room. It's the closest thing to a European-style dark room you will find in SF.
Thursdays nights are underwear night. It's not required, but a lot of guys do strip to their skivvies. There is a contest to see who is the hottest.
Smoking allowed in backyard patio (some action to be had there too)