After the insurance investigators are done viewing Ted's video (which exposes the man loading the snowmobile as a fraud), the camera then pans over to Ted at his desk. Before it can pull in to a closer shot the boom mic (and part of the boom itself) is visible at the top of the frame.
When Raymond is pointing the gun at Paul towards the end of the movie, the trigger is cocked in the first scene, then in the next two it's not, then he cocks it, but in the next scene it's again not cocked. Then it's cocked, not cocked, cocked and as he turns and shoots at Margaret the barrel turns as he cocks the trigger for the second time just before he shoots.
When Paul Barnell discovers the body in the dumpster he says, "911" and proceeds to dial three digits and you hear ringing. The tones the buttons make on the cell phone as the digits are pressed are actually "123".