Hellboy II: The Golden ArmyHellboy II: The Golden Army - Internet Movie Firearms Database - Guns in Movies, TV and Video GamesHellboy II: The Golden Army
Hellboy's (Ron Perlman) weapon of choice is the Samaritan, his massive hand cannon from the first film. He is seen using it multiple times to take out various creatures.
When Prince Nuada (Luke Goss) releases the Tree Elemental into the streets, Hellboy goes and grabs "Big Baby", a surprisingly even bigger handcannon in his arsenal than the Samaritan to take it on. It appears to be a six shot that fires two rounds at a time. Before firing it, he winds up the music box in the back, apparently to please Big Baby.
Members of the BPRD including Liz Sherman (Selma Blair) and Abe Sapien (Doug Jones) use Glock 22 sidearms, which is determined based on the muzzle diameters. Since the BPRD is a department of the FBI, it makes sense for them to use the Model 22, which is standard issue in real life.
According to the DVD commentary, the guns used in the auction house were not loaded with blanks, instead the actors mimed shooting and the noise and muzzle flashes were added later in post-production. This led to two problems during filming: first, the actors had to be coached not to "fire" the guns so rapidly, or else they were seen to be firing a ridiculously high number of rounds without reloading; second, Selma Blair had an unconscious habit of yelling, "Bang!" every time she pulled the trigger.
After Hellboy kills the Tree Elemental, police officers surround him and aim Glocks at him. Based on the muzzle diameter, they are likely Glock 21s in .45 ACP. They could also be Glock 20s in 10mm, but it is far less likely.
