Made by Gearbox Software and originally released in 2001 as an add-on to Half-Life, Blue Shift is a return to the Black Mesa Research Facility in which you play as Barney Calhoun, the security guard sidekick who helped Gordon out of so many sticky situations.
Really great game, nice atmosphere, and it has a nice HD Pack.
There is only one problem though, i finished it in less than 3 hours.