Other mistake: Towards the end of the film, after Snipes beats the crap out of a lot of vampires, Whistler throws Blade's sunglasses to him. They show him throw them in one shot, then in the next shot they show Snipes catching them. But look in the background at Whistler, he doesn't have the glasses, but is moving his arm like he is throwing them. The glasses must have been computer animated, and bad editing contributed to this mistake.
Trivia: Whenever you see Scud, he's wearing a t-shirt with the logo of the Bureau for Paranormal Research and Defence (B.P.R.D.). The B.P.R.D. is the agency that Hellboy, another comic book character, works for. Hellboy is the next movie to be directed by Guillermo del Toro, Blade II's director.
Trivia: As well as the Scud and del Toro Hellboy connections, Ron Perlman, who plays Reinhardt, plays Hellboy, and Mike Mignola, creator of Hellboy, helped create the look of Blade II as a concept artist. Del Toro and Mignola got together during the making of Blade II to talk about making Hellboy into a movie.
Question: Why aren't Nyssa and the other vampire fried by the big UV grenade? Sure, they dove underwater, but light doesn't diffuse THAT much underwater. I'm using the logic from an entry's correction that the UV light bounced around the corners is still enough to kill reapers, so it ought to kill them too.