Within the game's files are unused models for a red version of the robots seen in Mann vs. Machine (except for the tank and sentry buster), which can mostly only be seen by modifying the game's files. However, the red model for the robot Spy is used when a spy disguises itself. This could imply that players were originally going to be given the choice as to which team they would play as in Mann vs. Machines matches.

Robin Walker has stated that at one point that Valve team members would refer to Sticky Bombs as "winbombs", due to being perceived as too powerful by the team:

The Atomizer's original design was a simple re-skin of the Sandman bat, originally conceived with the name "The Atomic Punch". The name was likely changed to avoid confusion with Bonk! Atomic Punch.

The community created cosmetic item "The Danger" is a reference to the character Walter White from the television series Breaking Bad. This is further supported by the original workshop name, "The Chemist's Price". The name of the item is a reference to a quote from the episode "Cornered".

In the Team Fortress 2 short film "The Spoils of Love and War", during the scene in which the Pyro and Soldier are playing Rock Paper Scissors, there is a blueprint in the background of a capsule-shaped robot on a single wheel. This robot is the same as those used in the "Asteroid" map for the Robot Destruction game mode.

The community created cosmetic item "Crazy Legs" for the Scout is named after an old bug that would cause the Scout's legs to bend in an unusual fashion. It is also an alternate name for the Hunter from the Left 4 Dead series, of which inspired the item's appearance.

In Team Fortress 2's short film 'Expiration Date', during Scout's conversation with Miss Pauling near the start of the film, a keypad can be seen on the door behind him. When examined closer, the '1' key is noticeably dented when compared to the other keys. This implies that the combination for the door is some variant of '1111' - The same combination for BLU's intelligence room in Meet the Spy.

"The Southern Hospitality" is a community created weapon, which was released in the Engineer update. Shortly after the Mann-conomy update and the release of the Mann Co. store (where players can buy items for the game and their creators receive some money for it), the creator sent a thank-you letter to Valve co-founder Gabe Newell. He responded to this by buying 10,000 Southern Hospitality's from the Mann Co. store.

The Rooftop Rebel outfit set added in the Scream Fortress 2014 update through the Steam Workshop is a reference to the Hunter from the Left 4 Dead, and resembles the Hunter's design in Left 4 Dead 2.

In the original poster for the "Dr. Grordbort's Brainiac Pack", the "Eureka Effect" is called "Wrenchmotron 600", and the "Eureka Effect" is the name of the taunt used by the weapon.

The community-created cosmetic item, the Toowoomba Tunic, is a reference to the tunic that Link from The Legend of Zelda wears.

There are two unused models of the duck journal in the game.

The first is a yellow duck which isn't used in any of the styles.

Interestingly the second skin isn't implemented in the model, but the texture remains for it. It's set up to be paintable, and includes the phrase "Lets Eat!!!", a reference to the character Chica from Five Nights at Freddy's.

The Soldier is voiced by Rick May, the same actor who voiced Peppy in Star Fox 64.

The Gun Mettle update included a new taunt called the Kazotsky Kick, which lets the player perform a Ukrainian 'Hopak' dance. While the taunt is active a song will play, which was first heard in the Counter Strike: Global Offensive map "de_train". However, the version that accompanies the taunt features more instruments, has vocal chanting, and is about 1.2 times faster.

Several taunts present in the 2014 Love and War Update were already in the game files back in the 2013 Halloween Update, but were quickly removed in the following update.

Three of the Heavy's cosmetic items: "Carl", "Aqua Flops" and "Hunger Force" are all references to Carl Brutananadilewski from the Adult Swim TV show Aqua Teen Hunger Force.

There are 5 unused death sounds in the games files for the scrapped Civilian class.

There was a free "Tux" item that was only available in the Linux version of Team Fortress 2. However, it's possible to get the Tux item using a Windows version of Team Fortress 2 by changing the name of the operating system to any Linux distribution, such as Ubuntu, Debian, SteamOS, etc.

During the 2012 Pyromania update, animations of all nine classes burning alive were added to the game and never used. It is unknown why this was done.

The Scout exclusive taunt, The Carlton, is based of the character Carlton Banks from the TV show The Fresh Prince of Bel-Air, in which the character preformed the exact dance named after himself.