The Butcher's mask is a cosmetic in the steam workshop called The Stonefaced Slasher. It was made by Merczy for a cosmetic set named The Mute Maniac. It would be worn by pyros during Scream Fortress Events (Halloween).
During the scene where soldier finds himself in a war room and listens to the phone, the black and white scene and the decoration is a reference to the Stanley Kubrick film "Dr. Strangelove, or how I learned to stop worrying and love the bomb" (1964)
Each Mercenary is seemingly 'prescribed' Valium. Valium is used to treat anxiety disorders, or alcohol withdrawal symptoms.
The scene where Demoman shoots a zombie with a pistol is a reference to the 'Give Demoman a Glock' movement that happened within the early days of the Team Fortress 2 community. The movement asked for Valve to add the option for Demoman to use a traditional pistol as his secondary weapon instead of his usual explosive projectiles.
The penultimate scene in the movie, where Fritz escapes with the briefcase, is a reference to Mr. Pink's escape scene from the 1992 Tarantino film, "Reservoir Dogs". This is apparent in the almost identical camera shots, character movement and events. It should also be noted that the following scene in which Soldier kills one of the Mann brothers, is an obvious homage to the 1994 smash-hit "Pulp Fiction", which is also written and directed by Tarantino.