Just so we are all on the same page as it were, here is a list of books I do use on a regular (or even semi-regular) basis.
All RMFRP books, unless there is not an updated version (such as Essence Companion from RMSS).
In particular, Races and Cultures and Character Law. Point based talent and flaw selection.
10 million ways to die, RMSS weapons Law Firearms (but only for blackpowder weapons), ...and a 10 foot pole.
I do restrict the use of Fire and Ice, preferring to keep that kind of magic rare. So if someone wants to play a profession from that book, I usually only allow one per party (same for Arcane Companion from RMSS).
I do not use Martial Arts Companion, but see no reason why someone else might not. And aside for the training packages, I don't use the RMSS Races and Cultures - Underground book.
As far as races and cultures go, I do plan on doing new writeups for Arrylon. In the meantime, use the book as is, but don't use anything obviously monstrous (goblins, centaurs, etc.) or anything from Shadow World. Elven PC's should be discouraged.
So there you go...