razor kiss
When two people making out add razors to the mix. When they french kiss, the razors will cut their tongues and they will be able to feel tongue and taste blood at the same time.
Person 1: Look at those two vampire chicks razor kissing!
Person 2: That's hot... look at the blood dripping from their mouths.
Person 2: That's hot... look at the blood dripping from their mouths.