For the past couple of years I've been involved with Jailbreak: Source, a Half-Life 2 mod, as the lead programmer.
Jailbreak is a game mode that has been implemented on many game engines before us, so we decided to bring it to the source engine, along with some neat new twists and features of our very own.
The basic premise is of two teams, two jails and a whole bunch of weapons. The goal is to get the entire opposing team in to jail by killing them, upon which they will be executed in various gruesome and entertaining ways.
Sounds simple, but throw jail release buttons, devious jail escape routes and player upgrades in to the mix and you have a fast paced and intense game on your hands.
Below you can see the last two trailers that we released, demoing the current state of the mod: