Continuity mistake: Watch the first kiss scene between Reeves and Theron. Keanu's shirt drops to the floor, yet you can clearly see it on his shoulder in every other shot. The camera switches angles multiple times, so this is easy to spot.
Continuity mistake: Keanu Reeve's secretary reminds him of a 1 o'clock appointment at the DMV. When he arrives, the clock on the wall appears to read 12:20.