17. S.T.A.L.K.E.R.: Clear Sky
The prequel to the original S.T.A.L.K.E.R. follows the events that unfold before the second Chernobyl Nuclear Power Plant explosion, with players assuming the role of Stalker Scar, rescued by an independent Zone faction researching and learning about the irradiated area and the bizarre goings-on inside it. And it's just as ridiculously unforgiving.