Joe Cole, an English actor, has a very difficult time maintaining the "American" accent that he's affecting for the role. This is most noticeable when he speaks for more than a few seconds or is doing something physical as well as speaking.
The wounds on Kevin's arms were so deep that he would have bled out before the end of the film. While the duct tape used could has closed minor lacerations, the wounds shown were so deep that they would struck bone thus cutting arteries and veins.
When Pat fires the final shot (of 3 shots left), his handgun is left in the cocked position. Even if the gun were truly empty, the slide would not necessarily have to be in the eject mode (locked open). There are several reasons that a handgun slide could remain forward in the "cocked position" after the last round is fired and it is empty. Certain parts of the gun could have been replaced with aftermarket parts, or an aftermarket magazine could be used, both of which may not engage the "last shot hold open" feature. Also, certain grips on the gun would cause the slide release to be depressed while firing, possibly due to poor technique, which would prevent the slide from remaining open after the last round has been fired.
When Tiger plays a vinyl LP on a phonograph in Tad's apartment, he cues the record to the beginning, but the song that plays first is Track 7 of Side 1 of that album. Later, in a shot of the vinyl disc spinning silently with the needle all the way over to the disc's label, you can see that the disc has 5 medium length tracks, but the album supposedly played has 8 short songs on both sides. Though to be honest, we have no way of knowing how many records they played after the first one.
SPOILER:Even if the dogs were set upon the group and the accident was staged to appear to death by animal attack, their blood would have congealed by the time the dogs were brought in. Any pathologist would have been able to note that the bite woulds and flesh consumption took place post-mortem and that would have poked holes in the story that was being concocted.
The goof item below may give away important plot points.
When Amber fires the two shots at the enemy in the basement while he is fighting for control of the shotgun, it is obvious her gun is firing blanks as she fires two times in quick succession with no recoil at all.