Left 4 Dead II
 

will i been playing this game pass 2wks now.

there are whole serials I planning buy all of them, basic its Resident Evil Serials, there no story line to this game, you can play with other by LAN, Internet with other players

L4D 1 & 2

No story line, no maps,
limited to real life you running around trying Stay Alive with three other. it has Co-op too, you can use Steam Players/ friends members to with you invite with you too, like Delta Force game come playing with other players

source: https://store.steampowered.com/app/550/Left_4_Dead_2/

note its really cheap now dirt cheap too