When Nicholson guns down the bartender who had just been talking to Terry, the baseball bat the bartender is holding while being shot varies from being shot to pieces to being back in one piece again between shots.
When Terry and Kate meet in the bar with Jackie, Terry is smoking. The smoke can be seen when the shot is on Kate but there is no smoke when the shot is on Terry. This repeats throughout the scene as the camera cuts to each character.
Near the end of the film when Terry goes to Jackies apartment to tell him that he heard Frankie was involved in Stevies death, the Tequila bottle is on the window ledge on its side. After the scuffle between terry and Jackie, the Tequila bottle is upright.
Early in the film when Jackie introduces Terry to Irene in the bar, Terry has already ordered and is drinking a Guinness. A short time later, after Jackie and Irene leave, there is a slow motion shot in which Terry is now drinking what appears to be hard liquor from a rocks glass.
During the final shootout in the bar, the slide locks back on Frankie's gun. After he's shot, he falls to the ground revealing the slide forward. Not such a big deal in itself but the slide locking back was really illuminated during the previous scene.