Starsiege: Tribes, aka Tribes 1, is my pick. I played it religiously for the better part of my 20s, starting back when modems were frustratingly slow. I even played it competitively on ladders, using Capy co-founder Kris Piotrowski’s computer for matches because it actually had a videocard.
I love Tribes because it was a foundational shift in games. It helped me learn why multiplayer games were so special – because you formed a ten-person side in a Tribes match, quickly decided who was going to play Light Defence or Heavy Offence or ‘Cap’, spam Shazbot a few times, then try your best to function as a team. And you had to try to play as a team, or you lost. This wasn’t 1v1 Doom. This wasn’t Quake or
Team Fortress. This was huge, open maps, complex character classes and unbelievable movement, all of which funnelled into team play.
While Quake gave online FPSes the taste of speed, ‘skiing’ in Tribes blew it out. Initially a bug that became a core feature, skiing gave skilled players a path to traverse enormous open maps at Mach 10, and
maybe even grab a flag while they were at it. Prior to
Tribes, multiplayer games were played in corridors, in rooms, and in courtyards. Hell, in most cases they still are. And all of them were played exclusively on the ground. Quake’s Rocket Jump (all the way through to Tricking) explored additional movement space, but in a limited way. Tribes added a jetpack and gave players an entire extra dimension, to unbelievable effect, the impacts of which we’re still seeing today. There hasn’t been a multiplayer game since that hasn’t aped something, or everything, from Tribes. And there’s no game that feels better when playing with 20-plus players (even on a shitty modem).
My other picks were nostalgic, arsty, or mindbending. But I think multiplayer gaming is such a key piece of our culture, and I’m sure that Tribes changed it forever. Also, it was really damn fun.