Quake II
So then, why not find a source port for this one that also supports software mode? Yamagi is the answer.
If you've not tried Quake II in software mode, I suggest giving it a try. It doesn't make the game any more interesting of course, but you might be surprised by how different it looks. I always felt the colored lighting in 3d accelerated Quake II was too much—everything seemingly looks yellow or red all the time. In software mode, the colored lighting is turned off, and you get much more natural colors. This is noticeable in the main game of course, but it's especially noticeable in the expansion packs which look like completely different games. The difference is really night and day, almost like turning off weird post-processing filters etc. on modern games. It's not like Unreal, where turning off the colored lighting would seriously ruin the look of the game.