This is one of the most popular Doom source ports. It is available for DOS, Windows, Linux and Mac OS X, and should build on any POSIX platform which supports SDL. It enhances Doom with things like TCP/IP networking, OpenGL renderer, Heretic support and much more.
NES/Famicom emulator based on FCE Ultra.
An updated Mac OS Classic/Carbon-specific port of FCE Ultra 0.98.13, the Nintendo Entertainment System/FamilyComputer emulator, and beyond. This emulator is meant for older Macs, pre-OS X.