Warmod is a gamemode for Gary's Mod using the Fretta base, set in the Half-Life universe that tries to bring together sandbox, deathmatch, and RTS elements into a single cohesive experience that immerses players in cooperative and strategic combat.
Desert, currently on it's second incarnation, is one of the oldest, and most played maps around the office, and my personal favorite. Desert puts players in exactly that, a desert. Combine spawn in a combine base, while Rebels spawn inside of an old dust pyramid.