A s--tlist is a (sometimes literal) list of people who are on your bad side; if you anger your boss, for example, you might say that you're on his s--tlist.
The song was written by lead singer Donita Sparks, explains her s--tlist methodology in the song:
When I get mad and I get pissed I grab my pen and I write out a list Of all the people who won't be missed
Speaking with NME, Donita Sparks explained: "You should sing whatever you feel strongly about, whether it be drinking a lot of beer or rape. There's room for everything. Sure, we have a very long s--tlist, but everyone on the list deserves to be there. And it's not a personal thing, it's just human rights violators are on that list. Like Operation Rescue, who block off clinics so women can't get in to have abortions."
This song was used in the Oliver Stone movie Natural Born Killers in a scene where Juliette Lewis' character Mallory Knox plays the song on a jukebox and then kills a guy who is bothering her. "You made my s--tlist," she tells him.