Halo

I remember watching the 1999 MacWorld keynote webcast where Steve Jobs introduced Bungie Studios. They demoed a new game called Halo on a G3 Mac. It was Bungie's followup first-person-shooter to their other Mac-only hits, Marathon and Myth. After Microsoft's purchase of Bungie (to make Halo an XBox exclusive), the enormous Halo 2 sequel, and six years, they finally came full circle and released a Mac demo that I can download and play. It may not be as revolutionary as it would have been in 1999 but it's still a good game.