That is at once difficult and easy... let's see: I am going to follow the rules that Untimately followed: I have to own it and I value the content of the book. I am going to treat boxed sets as one single item.
- AD&D 1st Edition Players Handbook Premium Reprint (nostalgia & useable rules)
- AD&D 1st Edition Dungeon Masters Guide Premium Reprint (nostalgia & useable rules)
- AD&D 1st Edition Monster Handbook Premium Reprint (nostalgia & useable rules)
- Dark Sun Original Boxed Set (sentimental value, art work and innovation)
- World of Darkness Rulebook
- Vampire: The Requiem (most popular game in my gaming group)
- Dark Ages Vampire Limited Edition (if I keep it, I keep the best I have; I like Vampire: The Dark Ages better, but the mechanics are more solid)
- V20 Anniversary Edition
- Titan - The Fighting Fantasy World (original, not reprint)
- Out of the Pit - Fighting Fantasy Monsters (original, not reprint)
I am glad that Dungeon World isn't out yet, because it will displace one of those books.