STALKER Series, My favourite is Call of Pripyat, It's an FPS, open world game with rpg elements. Set in the area around the Chernobyl power plant disaster you're confronted by a world that has been changed by both the fallout from the Power plant and from illegal experiments conducted by rogue government agencies on both the local wildlife and humans alike. As well as the mutated victims of the zone there is a thriving community of fortune seekers known as Stalkers who hunt for artifacts that are created within anomalies in the zone and are of extreme value. There bases of operations offer a temporary safe haven where you can rest, eat, gather info and side missions and buy supplies. Real world weaponry and outfits are available, You will also have the opportunity to upgrade these items making them more adaptable and suited for the style of play you adopt.
The Stalker series also has an extensive modding scene so if you play and like the original games you can play again with minor or major changes.