Revealing mistakes: When Gina is in the hospital, we see the patient monitor in demonstration mode ("demo" is flashing). It also indicates the patient is an adult male.
Factual errors: When Fingers wants Pleasure to listen to some music, the remote doesn't belong to this type of B&O stereo. This stereo always uses a beolink 1000 remote.
Continuity: When Pleasure gives Happiness the gun, the cut on his face has only one bandage shown, but in the rest of the movie there are two.
Revealing mistakes: When "Fingers" shoots "Pleasure" in his apartment and and they show a close up on the ejected brass hitting the carpet, it is obvious that the brass is from a blank. It has the "crimped" end on it where it was sealed.