The addition of yet another free-to-play shooter to Steam wouldn't normally be news, but Dirty Bomb is being developed by Splash Damage, a UK studio that got its start developing mods for games like Quake 3, but earned real accolades with the launch of Wolfenstein: Enemy Territory. That too was a team-based shooter (and one of the first of its kind offered to players at no charge), and despite being over a decade old, still commands a loyal following of players to this day.
Before you click through to Steam to try Dirty Bomb for yourself, keep in mind that the game is currently only available as a closed beta test. It won't officially launch until "summer 2015." If you'd like to join the test, you'll need to register your pertinent information at the game's website.