Sven Co-op began life as a Half-Life mod over a decade ago, but it's finally got its own standalone release on Steam, after getting the all-clear back in 2013.
The best thing about Sven Co-op - other than its name - is that it's completely free. If you like that sort of thing - free stuff, that is - why not work your way through PCGamesN's list of the best free Steam games.
It's a co-op game where players can work through the original Half-Life together, although encounters have been tweaked to account for the extra players.
"While Sven Co-op is similar to Half-Life with similar weapons, monsters, and characters, the difficulty has been increased to suit team play," says Sven Co-op's Steam page.
"Sven Co-op's levels are set as missions and are generally separate from each other. Many missions span several maps and some are collected together in a series. The aim of most levels is to reach the end or to achieve an objective - obtaining a high score is not essential to beat a level, it's just part of the fun."
As well as being able to battle through the original Half-Life campaign, there are thousands of maps to play that have been built by the community over the years.
The standalone game will also include "many hundreds" of features, fixes and improvements, as well as new maps and content. All this, and Steam Workshop integration is promised to add more in the future.
Grab it now on Steam and you can play it for free, even if you don't own Half-Life.