Among the most overlooked valve games, Deathmatch classic is a quake-like fast paced shooter. The game is a lot of fun, but the servers look like Chernobyl in 2018.

The little known hardcore-multiplayer god version of half life is actually amazing. With its endless mod ability, unique combat, and addictive gameplay, this is easily one of the best arena games ever

Bringing " mod" to a whole new level, this game tears the boundary between being a sandbox game, and multiple games at once.

Eternal Silence is truly a game far ahead of its time. With tactical, immersive flight and infantry based combat, it feels a lot like an early attempt at what newer titles are trying to do.