Audio/visual unsynchronized: At the retreat you can clearly see the drummer not making contact with the snare drum. His brush is in mid-air.
Continuity: At the retreat, when Joy slaps the "Hello my name is Joy's Bitch" sticker on Chong's back, you can see it shift places and angles from shot to shot.
Continuity: The male stripper takes his shirt off twice.
Continuity: The position of Joy's hair changes when she quits her job.
Continuity: In the scene where Jack and Joy first tell each other why they're in Vegas, the ice in Joy's drink refills and empties depending on the camera angle.