Hazard: The Journey of Life is an incredible game/mod that can really mess with your head. IT forces you to break the loop of life, exsperiment with off things, and discover the meaning of life...
This game was started in 2007 and is still being made by the same single person. It was a complete MOD for Unreal Tournament 3, but is now a standalone demo.
Nothing about this game will make sense to you. You will find:
Auto-Decaying Walls
Disappearing Rooms
Halls That Lead to Nowhere
Going Backwards, To Find A Brand New Hall of Mind-F*ck
Frustrating Puzzles
Infinite Loops
And MORE!
Oh, and, all along the way, you will read amazing messages that will really tell you something about life.