Including #1, the 7th Sea Player's Guide
#8 Central Casting: Heroes of Legend
And #13, the aforementioned first printing of Deities & Demigods
Interestingly enough, one book not on list is one that I sold for literally hundreds of dollars (I had two, so I could afford to part with one), Central Casting: Dungeons.
That last one I'm particularly fond of, because I still use it to make up the occasional random fantasy dungeon.