During the monastery fight, Rayne throws one of her swords to save Sebastian. She is kidnapped, and the Brimstone guys leave to rescue her. Nobody retrieves her sword, yet she has them both back later in the movie.
During the Rayne's sex scene, the lovers are against bars in one scene, but not when the camera angle changes.
On the boat trip back to Brimstone HQ, Vladimir points out that if Rayne was just a vampire, crossing the water would kill her. Later on however, Domastir crosses the water with no issue at all.
All of the weaponry is blunt, with rounded points, making it as deadly as a butter knife. It's especially noticeable in the close-up when BloodRayne picks up her two hand scythes for the first time.
Rayne, a half-vampire who can be killed by sunlight, has a suntan.
Rayne has a modern tattoo on her lower back.
At 4:27, a man in the audience is wearing a modern wrist watch.
Someone mentions "Black Powder from China". By the 18th century, gunpowder had been used in Europe for over 200 years.