Buy, go on moddb, stalker anomaly, download. Literally unbeatable, one of the best gaming experiences i've ever had. Download boomsticks and sharpsticks if you want some more toys, honestly ignore the rep, if you're unsure, play on tourist and experiment. Once you get past the initial hurdles, one of the best games i've ever played.
Once you get the shotgun, dont drop it. Its the best shotgun in any game, period. Dont be put off by the horror either, the atmosphere is spectacular while not being overwhelming. If you can, play with headphones and on a high difficulty on high graphics if possible for the best action horror experience you'll ever get. Side note if you get an error saying disconnected or the game is failing to load into a new level, put all your graphics on low, then load it up then change them back, that should fix it, but honestly; play the main game, then extraction point, then perseus mandate and forget the other games exist. I cannot recommend this game enough, honestly one of the most cinematic, visceral, satisfyingly gruesome, atmosphere rich games ever released.