Bingo, cryENGINE; cryENGINE 3 is being used to in Project Contingency - a name similar to a level of Halo: Reach, Contingency, which took place years before the event of Halo CE. It's a fan made project with an open source, free-to-the-public engine, developed by Crytek. PC fans herald its completion. Kotaku recently posted an article (within the last 3 days) about Project Contingency's progress, but I admit that it was mostly a video.