The MTM 8, also known as the Loader is a robotic loader used in the Black Mesa Research Facility from the Half-Life video game.
Half-Life - MTM 8 Loader Papercraft

The Mk 2 fragmentation grenade is a weapon featured in Half-Life and its expansions.  It is a timed explosive that detonates five seconds after the grenade's pin is pulled.

Half-Life - Mk 2 Fragmentation Grenade Papercraft

Tektonten starts his Halloween papercraft project with this 1:1 scaled Skull from the Half-Life video game.

Half-Life Skull Papercraft

 

Tektonten jas just released the third installment of his HEV Suit papercraft.

Half Life 2 HEV Suit Arm Armor Papercraft

Here's an excellent model from Gollum999. Dog is Alyx's "pet" robot in the Half-Life 2 video game. This model is not for beginners. It contains 18 pages of about 381 parts. Dog papercraft stands at 31 cm high.
Half-Life 2: Dog Papercraft

Check out this 3D logo of the Half-Life 2 video game by the papercraft couple.
Half-Life 2 Logo Papercraft

This looks cool and creepy at the same time. Headcrabs are alien parasitoids found in the Half-Life video game series. They convert their human hosts into zombie-like mutants.
Half-Life Papercraft: Headcrab Mask

Tektonten has the full size HEV suit papercraft from Half Life 2 on his to-do-list but it will take a while to release the whole thing so he'll release 'em part by part. The Shin armor is now up for downloads.
Half Life 2: HEV Suit Shin Armor Papercraft

Teleportation (in many first-person shooter video games like the Doom or the Quake series) is one of the recurring themes of the Half-Life series. It was studied in the Black Mesa Research Facility, where functioning teleport were heavily used to travel to the border world of Xen, among others.
Half-Life Papercraft: Teleporter

That strange looking weapon is the 'Gravity Gun' (zero-point energy field manipulator) from Half-Life 2. It is designed for handling hazardous materials and is mostly used to lift heavy objects.
Half-Life 2 Papercraft: Gravity Gun

Here's a battery papercraft from Half-Life 2 by Masterman T.
Half-Life: Battery Papercraft

Alyx Vance's EMP Tool from the Half-Life video game series by Valve.
Half-Life: Alyx's EMP Tool Papercraft

Another helmet, this time from the Half Life 2 game. It's in pdo format with 13 pages of parts. Sadly, there's no texture.
Metro Cop Helmet Papercraft

Lots of cool models from this site. Get to build Vivi from Final Fantasy 9 and a gunblade from FF8. You can also download a couple models from Metal Gear Solid, a Pyramid Head from Silent Hill, rabbid from Rayman, a keyblade from Kingdom Hearts, Death Jr., a gravity gun and a couple more from Half Life.

Chamoo