If I can toot my own trumpet - I am quite proud of the Endurance mechanic in Endure - a survival game I wrote a while back.

The game is pretty much stripped down to this one mechanic. Players have a pool of points that they can spend to succeed on their tasks. This pool is pretty much depleting with every dice roll, and can only be recovered when PCs are able to get away from stress - rest for a bit, have a meal, sleep in a safe spot.

This leads to players playing the game more cautiously as the points deplete. Which emulates the PCs fatigue as they struggle through the adventure. More than that, the way you recover the points leads to the players actually doing many of the survival things that other games either skip or make it a chore. Because the game rewards the player for doing so, and does not penalize them for NOT doing it.