Here is one that we used to play back in the Lanning days. Signal Jammer, Katsin and Myself would stay up for hours playing this one.
Sven Co-op is a co-operative game originally based around Valve Software’s Half-Life. In this game players must work together against computer controlled enemies and solve puzzles as a team.
While Sven Co-op is similar to Half-Life with similar weapons, monsters, and characters, the difficulty has been increased to suit team play.
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.
Its free on steam right now! – http://store.steampowered.com/app/225840/
We are also running Sven Co-op servers in Sydney and New Jersey. They can be found in our server list or in game.