What was the first gamemode you played?

Mine was Spacebuild,
It blew me away and was what made me originally buy Garry's Mod, including all of valve's games at the time, which was a $100 bundle.

Just the fact that you could make a habitable spacecraft in a multiplayer game was incredible.
No other gamemode will come close and I hope I can work on a port of it for s&box one day...