Crystal meth hunter
A crystal meth hunter is a gay man who, though not necessarily a drug user himself, seeks out meth-addicted men within the gay community for sex, for the reason that meth addicted men will go much further, sexually, than anyone not addicted to meth.
"Hey, you see that guy cruising the dance floor? He's a crystal meth hunter, only tweaker dudes will do the perverted things he likes.