I lowered the graphical quality of Half-Life 2 by a huge amount, and this is the result. I'm sorry for jumping around too much. Also, I forgot to disable vertical sync, so the whole time the game was running at a solid 60. I have no idea what the capabilities where beyond that if I had removed the cap.
The settings used were:
I compiled that list together from various videos I found, as well as from messing around with all of the commands beginning with "mat_". Some of the strange effects you see are probably easily removed with no performance impact, so if you find anything, comment about it.