Better yet, any source code that was released by ID software.
You can find it all, here:
https://github.com/id-Software/Quake-2
It is so incredibly clean, elegant and pushes everything out of the C programming language including some Godlike pointer hacking and bit field manipulation. Function pointers and callbacks are made to look smooth.
This is the work of the programming God John Carmack and his team Brian Hook and George Cash.
The opinions are not new, this article outlines the beauty of Doom III's source code:
The Exceptional Beauty of Doom 3's Source Code
These guys were magicians and I aspire to be like them one day.
