Other mistake: When the tank falls through the hole in the bridge, the tank's occupants are impossibly shown to be clinging to the edge of the hole at the same time the tank is going over the edge, as if the tank and the occupants were occupying the same space.
Continuity mistake: When Storm is teasing Gambit for damaging the pool table, she is holding a television remote in her left hand, which is yellow (Storm doesn't wear gloves). A couple of shots later, she is holding the remote in her right hand (she had time to transfer the remote to her other hand, so no mistake there), which is colored correctly.
Continuity mistake: When Rogue and Gambit are playing pool and Rogue is getting ready to try and sink the 8-ball, the cue ball is shown to be close to the corner pocket and its rail. When the shot changes, both balls are suddenly further away from the pocket and the rail. It's an instantaneous change, so it can't be a matter of the cue ball rolling.
Continuity mistake: When Cyclops forces his way to the front of the crowd to confront Warren Worthington (Mystique in disguise), the Lady Gardener is standing just behind the mutant with the bowl-cut hairdo. When the shot changes, the two are suddenly standing next to each other.