First up: Excalibur: Morgana's Revenge
Originally a total Mod of Bungie Softwares Marathon 2, with has since grown into a standalone FPS.
A decent game, somewhat hard at times, but polished and very playable.
(Note: versions available for Mac, Linux, and Windows.)
Links:
Authors Site
Wikipedia Page
Number Two: HACX
Formerly a commercial DOOM 2 addon WAD, now release for free.
Used to require DOOM 2 to play, but the newest version is a standalone.
Don't know to much about this game, I personally have not played it.
But it seem to hold a pretty good reputation around the Doom Wad community, so it might be interesting.
Links:
Game Site
Wikipedia Page
Number Three:
Inner Worlds
Released as a Shareware in 1996 by a company called Sleepless Software.
They went bust do to advent of 3D in gaming.
Their company web page says that they have decided to give the game away for free.
The game itself is akin to Castlevania, a 2D fantasy platform game.
It is a DOS game, and will require DOSBOX to run under modern systems.
Links:
Company Page
Wikipedia Page
A little history of the game
Thats all for now, hope this is

Edited by Red Fortress, 15 April 2011 - 09:59 PM.