Mixom

Mixom Tools (or simply Mixom) is a company in later ID Software Doom games, such as Doom 3, and the reboot.

Doom 3
Shown as a supplier of several different technical tools, devices, and office furniture. During the story, Mixom mistakenly ships a number of chainsaws to the UAC base on Mars, in place of the requested jackhammers.

Looking closely in some cutscenes the player may be able to see the Mixom logo on the side of telephones around the UAC base. It also occurs on doors, some computer terminals, Portal pads and other devices. Upon Marine's First arrival in Hell, The broken portal pad can visibly read "Mixom". Additionally, a newsreel plays on a TV early in the game (before all hell breaks loose) about Mixom and its rival company comically named, Moxim suing one another for various reasons.

They also make 'Mixom bolts', 'Mixom seals' for windows which are much cheaper than Moxim brand products.

Doom II RPG
Mixom appears again with a number of new products. Including the Mixom Glaevenscope which checks health vitals.

Mixom tech to work on Septic system tanks.

Doom (2016)
Mixom returns in the 2016 reboot of Doom.

The earliest plans for the formation of the Martian colonies began over a century ago (before 2149). It wasn't until the UAC involved itself in the late twenty-first century, acquiring key personnel and territorial rights to the majority of the planet's surface, that the plan would finally evolve into an achievable enterprise. Partnering with MIXOM (which would over time build its reputation as the world's most trusted interplanetary supplier), the UAC developed the first-ever trade route between planets.

For nearly a century UAC and MIXOM (with the help of third-party contract organizations such as I/O Logistics would lay down the Foundation piece by piece, for a new civilization on the barren planet. The endeavors countless contributors have assisted in the construction of the Argent facility and all of UAC's operations on Mars.

They are the manufacturers of the various doors on the UAC site, as well as Mixom Oxygen Synthesizers. It's possible to also find it's rival, Moxim's doors, and products as well.

Mixom Manufactured is also revealed to have manufactured Soda dispensing machines, alcaholic dispending machines and Hot Food Express machines, and external (outside) walls aswell.

Trivia

 * Mixom Tools is most likely a Japanese based company, as the Doomguy eventually finds an e-mail which refers to a Mixom website, Mixom.co.jp (the link is dead in the real world). .jp is an Internet country code top-level domain for Japan.
 * In Rage, Mixom is featured as a remnant of the old world, operating a chain of gas stations among other things. It is one of several hints within the game that seem to indicate it occurs inside the same universe as Doom 3.