The cellphone ringtone that Hertz uses for his wife is 'Ride of the Valkyries' by Richard Wagner. A subtle indication of the nature of their relationship.
In the beginning of the movie, during the rooftop scene, where Clive Owen's character shoots the neon sign to spell out "fuk u", he says "Fuck you, you fucking fucks." That line is taken from the lyrics of the Strapping Young Lad song "You Suck". The band later appears in a music video, on a television.
In the final scene at the café, a fat guy is sipping his
milkshake having more than half of his glass empty. When Smith, angered by a row of irritants, starts shooting, a bullet breaks a fat guy's glass, which is surprisingly full. Also the type of glass is changed: the full glass, which exploded was not knurled, but smooth from the outside. (It also makes you wonder what the trajectory of the bullet was and where it ended up.)
In the scene where Mr. Smith jumps off the bridge, he shoots a few holes in the top window of the car, but as you can see, in the scene where he actually jumps through the window, there are no bullet holes.
Mr. Smith: [after a shootout with several men, and shooting out letters of a neon sign so that all that's left says "FUK U."]
Fuck you, ya fucking fuckers.
Opening shootout / birth scene - "Breed" by Nirvana.Rooftop shootout - "Joker and the Thief" by Wolfmother.Smith enters brothel - "Dirty Laundry (Skeewiff Remix)" by Bitter:Sweet.DQ's introduction - "Money" by Jesca Hoop.The music video on TV that Oliver likes - "Zen" by Strapping Young Lad.Smith's warehouse shootout / jump down staircase - "Ace of Spades" by Motorhead.Band playing in metal bar - "Landscape" by Marr.Smith and DQ have sex - "Patient Eye" by Midnight Movies.Sex shootout - "Coral Den" by Midnight Movies.Gun factory shootout "Warehouse Shootout" by Paul Haslinger.Car chase - "Switch On" by Paul Oakenfold.Smith jumps out of the plane / freefall shootout - "If You Want Blood, You Got It" by AC/DC.Smith escapes from torture room - "Private Hell" by Iggy Pop and Green Day.End scene / end credits - "Kickstart My Heart" by Motley Crue.