Valve Corporation

Background
Valve Corporation, also known as Valve Software, is an American video game developer and distributor that was founded in 1996 in Bellevue, Washington by former Microsoft employees Gabe Newell and Mike Harrington. They are best known for their 1998 debut product Half-Life and its sequels, the Source engine used for production of their games, and the Steam digital distribution platform. They are also known for the Counter-Strike series, the Team Fortress series, the Left 4 Dead series, and the Portal series.

1st Logo (1998)
Logo: We zoom in over the exterior of a big dark gray building (sort of like a jail or factory), and go through one of the windows. We see a shirtless bald man wearing long pants (mrvalve.mdl) getting ready to pull a lever that starts up a letterpress-esque machine. He puts his profile on the base and when the press (which has the Valve logo on it) goes over his head, it plants a dark red valve (spiggot.mdl) on the side of his head. He gets up, strangely without any ache or pain whatsoever as if nothing happened.

Technique: 3D animation.

Music/Sounds: A portion of the ambient/trip-hop track "Hazardous Environments", composed by Kelly Bailey for the company's first video game, Half-Life.

Availability: It was only used as a tech demo for the GoldSrc engine.

2nd Logo (November 19, 1998-June 1, 2006)
Logo: On a black background, we see a fading-in sepia tone picture of a young man with black slick back hair with a goatee looking at the camera with a valve sticking out of his left eye. After the picture fades in, an box outline fades in the bottom right corner of the picture, containing the word "VALVE" where the "E" is a superscript. Both the picture and the text then fade out slightly faster than the speed they faded in.

Trivia: The logo itself was designed by Gabe Newell and Ray Ueno. The man in the picture was a former Valve employee (possibly Mike Harrington). Both this picture of the man and the picture used in the next logo were taken between 1995 and 1996. The concept for this logo is "Open Your Eyes".

Variants:
 * There is a variant where the picture is zoomed in to fit the screen.
 * Starting in 2004 with the release of Half-Life 2, the color of this logo has been toned down from its original sepia, the fade-in and fade-out are smoother, "trembling" effects are added to the photo and copyright stamps follow the fade-out.

Technique: The picture and text fading in and out, the intentional choppiness.

Music/Sounds: A fragment of "'Hazardous Environments" plays.

Availability: Rare.
 * Seen on the non-Steam, original CD versions of Half-Life and Counter-Strike. The color down-toned variant is seen on the original Half-Life 2.
 * Sadly, Steam versions of Half-Life 2 use the next logo, while Steam versions of Half-Life and Counter-Strike have no logo at all.
 * It can also be seen on the Xbox versions of Half-Life 2, Counter-Strike, and Codename Gordon.
 * This logo was going to be used in Counter-Strike: Condition Zero (as evidenced by this logo's AVI file inside the game's directory), but never ended up being used for some reason.

3rd Logo (October 10, 2007-)
Logo: On a black background, we see a fading-in sepia tone picture of a man's bald head (with most of his head and face silhouetted by darkness) with a valve sticking out of it. Similar to the previous logo, after the picture fades in, the Valve logo fades in at the bottom left corner of the picture. Both the picture and the text then fade out slightly faster than the speed they faded in. There are more trembling effects than in the last logo throughout.

Trivia: The man in the picture was randomly picked off of the street to pose for this picture. His name was never verified. This logo's concept was "Open Your Mind". This picture was used on Valve's website as early as 1998.

Variants:
 * Like the previous logo, a variant exists where the picture of the man is zoomed in to fit the screen.
 * On the Counter-Strike: Global Offense beta, Dota 2, and the Steam version of Portal 2 (after the Perpetual Testing Initiative DLC release in May 2012), the man in the picture (slightly more live-actioned) briefly turns his head towards the camera near the end of the logo before cutting back to normal. The picture also fades in and fades out at the same speed. In addition, the Valve print logo (with the box outline and the letters now in a color) doesn't fade into the picture or fade out with the picture, it instead fades in and out (via a "wipe" effect) by itself after the picture fades out.
 * On the Free to Play movie, the "Turning Head" variant is cut to the point where the Valve logo fades in and out.

Technique: Same as before, but the trembling effects are increased.

Music/Sounds: Same as before. On the variant, the music is edited.

Availability: Seen on most of the Valve games from The Orange Box onward. The "turning head" variant appears on the aforementioned games above.

4th Logo (VR Variant) (April 5, 2016)
Logo: In a room filled with valves, we see the Valve logo in white and 3D. Everything that happens involves you looking around in your VR headset.

Technique: You moving your head around with the VR headset. Otherwise, the whole room gradually lights up and smoke emerges. You can actually touch the valve that is hanging on the platform that you're standing on, but it doesn't do anything.

Music/Sounds: Eerie factory sounds, mixed with the same fragments of "Hazardous Environments" from the previous logos.

Availability: Seen on The Lab. It is not seen on Half-Life: Alyx, instead being replaced with the 6th logo.

5th Logo (November 28, 2018-March 1, 2022)
Logo: We start off with rapidly flashing footage of many Valve games, which zoom out in a box on a black background. The box glows and stretches horizontally as letters of the "VALVE" text fly towards it. The footage fades to white and the glow effect fades out. The logo transitions to the opening of the game.

Variant: On Aperture Desk Job, the logo is still.

Technique: The footage and the text.

Music/Sounds: The opening theme of the game.

Availability: It made its first appearance on Artifact, and has recently appeared on Aperture Desk Job.

6th Logo (VR Variant) (March 23, 2020)
Logo: Similar concept to the 3rd logo, now in 3D. In a dark room, we see the same bald guy from that logo fading in, however now in 3D and in a much darker environment. The Valve logo is also shown, this time being completely filled in with red. The guy slowly turns his head as the logo fades out.

Trivia: The guy can be viewed as a model in HLMV (Half-Life Model Viewer), included with Source SDK and Source Filmmaker. You can see his face, which shows whited out eyes, indicating he is blind.

Technique: Similar to the 3rd logo, however now in 3D and without the trembling effects, and you moving your head around with the VR headset. Really nice modeling work done on the logo.

Music/Sounds: Same as the third logo.

Availability: Current. First shown on Half-Life: Alyx and may be shown on newer VR games from Valve.