Consider this a recommendation for the entire STALKER series so far (latest as of this being Call of Pripyat). The STALKER games are FPS/Survival Horror/RPG hybrids where the emphasis is on the FPS gunplay and the survival elements.

You can get thirsty or hungry or need sleep and have to manage those needs alongside that of the deteriorating conditions of your weapons and armors. Ammunition, food, and drink needed to survive are scarce, but can be traded for with almost anyone if you have the right amount of goods or money to sacrifice for it. The game has large maps you can travel between like a sandbox game, and the gunplay is some of the tightest I've seen with really good gun physics. The games also have a wildlife simulation system similar to the one in place in FarCry 3 in a way; animals and mutants will run around and do their own thing after they spawn and kill each other (and maybe you) for survival or food.

Despite the large amount of freedom these games afford you to carve your own path, they feel very focused and are best approached with a strategic mindset.