So I got curious and bored one day and I made this
http://www.GHWChronic.com/pev_research.php
It's a listing of all of the pev variables. I have filled in as many blanks as I can hopefully as accurately as possible. I know a lot of people on this forum know plenty more than me about the HL engine and what these variables do.
At the bottom of the page you can add notes and I will modify the table as notes are added.
Spam will be filtered.
xPaw:
Link above is currently dead, and you should use this replacement:
https://github.com/xPaw/PevResearch