The director/producer originally planned to shoot the high school scenes at Grosse Pointe South High, but did not get permission from the school board. They felt that it would be inappropriate to show someone graduating from Grosse Pointe's school system to become a hit man.
There are several Bond movie references, including the attempted poisoning by string (You Only Live Twice (1967)), and the Guns N Roses version of the theme from Live and Let Die (1973) which Martin listens to just before enters the Ultimart for the first time (when he enters the Ultimart it changes to a Muzak version of Live and Let Die that picks up exactly where G&R left off). There are also references to Goldfinger (1964)
The arcade game that the Ultimart employee is playing during the shootout is the aptly titled classic Doom II. The game was never actually available in a commercial arcade cabinet and must have been constructed specially for the film.
When talking to the prospective home-buyers, Martin says he has always felt "kind of temporary" about himself. This is the same thing Willy Loman says he feels when talking to Ben in "Death of a Salesman."
When Minnie Driver tells John Cusack in her bedroom that he's a "...psycho," she can be seen moving her hand as though talking. In an interview, Cusack said that this was an ad-lib, as she had seen John and Joan Cusack doing something similar with each other on the set, off-camera.
When John Cusack first goes round to Minnie Driver's house she says, "You can't come in," in a Jamaican accent. This is a reference to the song which is playing in the background - "You're Wondering Now" by The Specials, which starts off with a knock at the door followed by one of the band saying the same thing in the same (albeit more authentic) accent.
When Martin (John Cusack) is trying to protect Debbie's father, Grocer (Dan Aykroyd) can be heard downstairs reciting a passage from the Bible. It is from Revelation 13. "And they gave worship to the dragon, because he gave authority to the beast; and worshiping the beast, they said, Who is like the beast? and who is able to go to make war with him?"
The only shot of Grosse Pointe is the aerial shot of the road next to the lake (Lakeshore Drive) with Grosse Pointe South High School's bell tower visible in the background, the only actual shot of the school.
When Marcella tells Martin about the offer in French about taking out a Greenpeace boat, it's a reference to the 1985 sabotage of the Greenpeace yacht 'Rainbow Warrior' in New Zealand by two French Secret Service agents. The yacht was to lead a fleet to protest French nuclear tests in the Pacific before it was destroyed by the French agents. One Greenpeace photographer died aboard the ship during the sabotage mission.
During the scene where Jeremy Piven first sees Martin, he brings Cusack over to his BMW. His BMW is parked in front of a red zone, even though his car is the only one that is on the curb and there are plenty of legal spaces for him to park.