In Blade II, there's a scene where it's pointed out that vampires can see quite well in the dark. In the opening of Blade: Trinity, when the vampires find Drake's resting place, they use numerous lighting devices to see in the dark caverns.
As the vampires get out of the helicopter in Iraq one holds an M60 Light Machine Gun, a belt fed weapon but the weapon does not have any ammunition link going into it. There is no belts of ammo anywhere on the vampire and nowhere for him to carry it. Why carry a weapon with no ammunition?
When Blade jumps out of the window after collecting his sword from the police station a large amount of glass hits the floor where he lands. When we cut back to Blade kneeling where he landed, the smashed glass has disappeared.
At the beginning of the movie we see Blade being filmed while he shoots the ersatz vampire. Just before Blade runs away from the "murder scene" we see the photographer put the camera down and start laughing. But, when we see the film on the computer screen, we see Blade running away.
In the beginning of the film, we see Blade running from the body with the spotlight following him. When the lady with the camera reviews the DVD, it shows Blade running away while the spotlight stays on the corpse.
When Blade is imprisoned, the psychiatrist questions and mocks him. When the camera is besides the psychiatrist and facing Blade, you see that Blade keeps his head turned to the right, so he has to look through his left eye corners to see the psychiatrist. But when the camera is located behind Blade, facing the psychiatrist, you can see that Blade is looking straight at him. This changing of the angle happens several times during the conversation.
After Blade jumps his car out of the semi in the beginning chase scene, he jumps over the tailgating car. When he lands and is shown burning rubber in reverse, the car he just jumped over is no longer behind the semi.
When the Nightstalkers first take Blade to the Hideout and are showing him the Daystar virus, Abby doesn't have her archery sleeve on. In the next scene where they go visit Hedges in Weapons, Abby's sleeve is back.
In one of the motorcycle street shots halfway through the movie, on the left of the screen the stationary camera clearly shows the sign for the Vancouver City Police's East Hastings detachment, including phone number.
When Drake is taking his first walk in the day, the traffic stops at the red light and you can see the news van for City Pulse news, a local Vancouver station.
Two Canada Post trucks can also be seen in the intersection.
The goof items below may give away important plot points.
(Theatrical version): When SWAT members come across the body of Drake disguised as Blade at the end, when the camera pans out the window it clearly shows Blades vest, red shirt and the large distinct silver buckle w/logo. When it pans back in from the overhead vantage, he is in Drake's outfit, naked from the waist up.
When Hannibal King accidentally falls through the skylight after killing the vamp dogs, he bangs his head on the bar than runs across it, slightly bending it. When the SWAT cops storm the building soon after, the bar across the skylight has no bend in it.
During the fight between Hannibal and Danica near the end, Danica throws Hannibal through a painting. When the camera concentrates on Hannibel, Danica is seen walking in front of the painting in the background, however the next shot, which concentrates on Danica, shows her walking from behind the painting.