Dementor's Kiss
While kissing french or otherwise, one partner will suck the air (soul) out of the other partners mouth and lungs. Also effective in sucking the happiness out of the room.
Steve: If I know I'm not getting any with a girl, I'll give her a Dementor's Kiss.

Dave: What?

Steve: I'll kiss her so I can suck all the air out of her and kill the mood even more.

Dave: What does that do?

Steve: don't know if I'm not getting laid it's just fun.