Marathon came out in 1994, and was the first game ever to have dual wielding and the first game ever to have an in game voice client in multiplayer. It also had grenade hopping, the first of it's kind, although quake a few months earlier introduced rocket jumping. It was also the first Shooter where NPCs moved around and talked. The game is/was as important as Doom, Quake and Wolfenstien 3D. Marathon, Marathon Durandal, And Marathon Infinity are all from he mid 90's and were made mainly on Mac, but Durandal was also on PC. Now they are open source, and all available in Windows/Mac/and Linux. Back then Bungie was a Mac games developer, and Halo was originally going to be a RTS game based on the Marathon Universe, then It was going to be a ybrid FPS/RTS, then Microsoft bought Bungie and changed Halo to a FPS for Xbox instead of a RTS for Mac.