Dark Sector, the 'original version' of Warframe, is currently free on Steam
Back when Digital Extremes were largely known for collaborating with Epic Games on the Unreal Tournament series, they made a little game called Dark Sector. Released in 2008, it's part of the fine tradition of post-Gears double-A actioners that basically consist of taking a gruff man, throwing him into a world of grit, gravel and burning oil drums, and handing him a murderous gimmick. Dark Sector's gimmick was the glaive, a pointy boomerang you could use to scoop up objects, solve puzzles, and kill stuff in third-person view.