Warner Bros. Interactive Entertainment announced today that their fast-paced downloadable shooter, Gotham City Imposters, is now officially free-to-play on Steam.
As of today you can get on Steam and download the title, as well as all of its expansion packs absolutely free. As the game already supports microtransactions, it seems like this will be a fine strategy for helping increase a surely shrinking player base (and also making WBIE some money in the process.)
The only question that remains is whether the console versions will make the F2P jump as well. Given XBLA's recent propensity toward experimenting with that business model, it seems like this would be a perfect match.