Teeworlds

Teeworlds is a 2D shooter / jump n' run game that is open source. Due to this, there are many community gamemodes, which kept the community alive all the time since 2006. Examples of gamemodes range from blocker, xPanic, zombies, fng and gores.
Teeworlds has cute little characters, called "Tees"

"Hey, wanna play some teeworlds?"
"Sure, let's go on pepe. ChRIstMas`iPro and the clan has been killing it there recently"