Hard to believe, but after 12 years of community development, the guys from the open-source engine based on
Bungie's Marathon trilogy Aleph One have finally released
a version called 1.0!
If you are lazy, you can watch this first part of a long set of "let's play" videos to get run through this FPS classic:
But honestly? This thing even runs on your cell phone (unless you have a talking brick like me :p ), so no reason not to play it yourself.
Edit: *hust* that was shoddy investigative journalism by me
again :( In fact Aleph One does not seem to run on cell phones
yet.