Steam, Valve’s digital distribution service, has come a long way since it officially launched in 2004. Back then, players fretted about having to install a weird DRM service just to play Counter-Strike and Half-Life 2.Now it’s the premier digital platform for game sales and online play, accounting for 75 percent of online PC games sales worldwide (although others, like GOG, are nipping at its heels).

One of the great things about Steam, though, is that there are tons of games available on the service that don’t cost a penny to play – just by having a Steam account, you can play dozens of quality games, many of which are multiplayer. Sure, there are a few that let you pay money to buy, say, hats for your in-game characters, but here are our ten favorite games on Steam that won’t require you to spend a nickel.