Continuity mistake: After Marcus kills Kraven, we cut back to Selene and Michael. As he talks about her saving his life and that how everything has changed, part of Selene's fringe switches from hanging in front of her face to tucked to the side between shots. In the closeup shots it hangs in front of her face and in the wide shots it is tucked to the side.
Continuity mistake: In the scene where the helicopter is outside the castle, the entry team dons their diving gear to enter the water. They put on gas masks with one viewing panel. When the shot changes to a water view the entry team is wearing scuba masks, which have their viewing panel divided in half by a black line. When the team emerges from the water within the castle in the next shot they are back to wearing masks with one window.
Continuity mistake: After the fight on the barge between Michael and Marcus, Selene tries to revive the impaled and seemingly dead Michael. At one point she rips his shirt open to pour her own blood into his wound, then the shot changes to her face, then changes again, slightly further out. It is in this shot, you can see Michael's shirt is still intact.
Continuity mistake: When Michael is being shot by the police, Selene can hear the shots very clearly, despite being down in the basement off the safe house. She goes out and goes towards the shots. Although she's much closer to the action, and outside the building now, the shots seem a lot further away.