(at around 1h 9 mins) Detective Sebastian fires a total of 7 rounds at the Antigen van in the parking garage - three at the driver, three at the front-left tire, then one after it passes him - without reloading, yet the Taurus Judge pistol he is using is designed to only hold 5 rounds in its cylinder. Later, after Sebastian has reloaded the pistol, he fires 8 rounds at Dr. Lane, again without reloading.
(at around 37 mins) When Eve wakes up, her white dress has no blood on it. In the next screen, her white dress has the blood on it again.
She fires thousands of bullets during ending scenes, where did she get the extra-ammo?
All modern elevators have safety systems to prevent their fall should all lifting cables be cut. Elisha Otis invented this back in the mid 19th Century.
(at around 1h 1 min) Selene gets shot in the back repeatedly when entering the building yet there is no damage to her coat or corset.
(at around 1h 14 mins) During the fight in the parking garage at the end of the film, the sound of one of the guards screaming comes after his head has been cut off and hence separated from the lungs, which would make a scream impossible.
(at around 1h 6 mins) When Det. Sebastian is watching the security videos, we see a shot of Dr. Lane taking Eve down a hallway, with the security camera preceding them down the hall (moving with them), rather than panning to follow them as would be expected from a fixed-position camera.
(at around 26 mins) When David and Selene are being chased in a van by Lycans, the pedestrians walking on the sidewalks don't react at all to seeing the Lycans running past them or causing cars to crash.
(at around 1h 6 mins) When watching the footage of the security camera on the security monitors in the 3D version, the Time and Date stamping on the footage is in 3D. If it were in real life this would all appear as a flat 2D image on the screen.
Why would Eve have a British accent? The script states she was never out of the lab before the start of action in this film, and no one around her spoke with one.
(at around 27 mins) When Quint stops to inspect the dead Lycan on the road, the camera is reflected in the windows of the car as he drives off.
When the Lycans attack the vampire's coven, an earplug is clearly visible in one of the vampire's ears.