1st ed core books, DDG (inc Nehwon & Lankhmar
S1-S4 compendium, B1, B2, C1, G3, D3, UK4, I1, I6, L1, WG4, X1, X2
White Dwarf 1-86
RQ2 mainbook, Cults of Prax, Cults of terror, Trollpak, Pavis, Big Rubble, Borderlands, Griffin Mountain
Coc rulebook + investigators' handbook, Delta Green, Masks
D&D5E Rulebooks + Xanathars

CP2020
Night City supplement
Crypts & Things
Beyond The Wall
Vornheim
Silent Legions
ZEFrs
Apocalypse World
FATE
GURPS

Quote from: Fortunato;1112909I can't even do it in my head

My tomb will have bookshelves.

That would be a very sweet tomb, indeed!

Welcome to therpgsite, Fortunato!

I moved across country a couple years back, into a smaller house. I fought tooth and nail to keep my RPG collection intact, and succeeded, but I did consider the question back then.

Absolutely would keep in any move:

D&D Rules Cyclopedia
AD&D 1e: All "core" products and setting-agnostic rule supplements, the Adventures hardcover setting books, the Mystara Gazeteers.
AD&D 2E: All "core" products and setting-agnostic rules supplements. All black-book setting hardcovers. The core box set each for Dark Sun, Spelljammer, and Birthright. The complete run of Birthright splats.
Hackmaster 4E, all of it.
Hackmaster 5E, all of it (Which doesn't amount to much)
Warhammer Fantasy 1E core book
Warhammre Fantasy 2E - Core book, all the rules supplements, all the outside-the-Empire setting books.
Shadowrun 1E, 2E, 3E: All that I have, which is sadly less than I would like - about two dozen books total.
World of Darkness (The Original): The core hardcovers for all the settings, plus the Dark Ages line, Sorcerer's Crusade, Werewolf: Wild West, etc. The complete Kindred of the East line, the complete Changing Breeds collection, all of the stand-alone mini-core books like Demon Hunter X and Sorcerer. I do wish, here, that I had the money to buy the bound, physical releases of the 20th line, but I don't.
Dresden Files: Your Story and Our World both
The Laundry Files - All of it

All this stuff... somehow I would make room for it. If I had to stick it under my bed, or something.

There are a few things I wish I had print copies of. The 20th line of WoD I already mentioned. Shadows of the Demon Lord, a few other things. But since I assume I'll have my computer, that's not a huge deal.

Now, if we're talking "Bugout bag" type scenario, like... The world is ending, I need to grab a few books to keep us sane with in our survival bunker? Some situation like that?

AD&D2E: The Core Three
World of Darkness: Mage, Vampire, Werewolf, Changeling
Shadowrun 3E - Not my favorite incarnation of the setting, but some of the best rules.
Dresden Files: Your Story
The Laundry Files - Just the core.

If I had to trim it even further, I could probably fudge (no pun intended) World of Darkness with Dresden Files... I did some preliminary work on that a few years ago when it first came out. Probably could do something Cthulhu-ish with it, and something Cyberpunky too, but those would be harder. So I'd hang on to The Laundry Files core book and the Shadowrun 3E core book.

Definitely keep:

• All my Traveller material
• All my Fate books
• All my PDQ books
• Mythras and all supplemental material.
• Hollow Earth Expedition
• Beyond the Wall and Other Adventures
• Solar Blades and Cosmic Spells
• Old-School Essentials
• Setting books, because I'm a sucker for setting material

Possibly keep:

• D&D 5e
• Call of Cthulhu
• Runequest: Roleplaying in Glorantha

Definitely toss (mostly because I don't play them and they take a lot of space, not necessarily because I don't like them):

• All the World / Chronicles of Darkness books.
• All my Gurps books.
• D&D 3e & 4e

Quote from: Fortunato;1112909I can't even do it in my head

My tomb will have bookshelves.

This is my kind of answer.

Desert island scenarios are always fun. But it's weird to think that there is simply no scarcity of texts anymore, when you can fit thousands of PDFs on a USB stick. It's hard to wrap your head around as we (let's say, those of us over age 30 or so) are the generation in history who lived throught the one-off transition from paper and scarcity to electronic documents and the cloud.

I'm at the point that I could toss my entire shelves and just play my own RPGs. It would be the perfect incentive to actually finish the damn books instead of leaving them languishing in playtest mode.

The more I consider this idea, the shorter my answer becomes.  Truth is; the game is more in my head, than in the book.

Quote from: Spinachcat;1113087I'm at the point that I could toss my entire shelves and just play my own RPGs. It would be the perfect incentive to actually finish the damn books instead of leaving them languishing in playtest mode.

I don't have full-on homebrew RPGs to write, but I agree with the spirit of what you say -- I've internalized enough rules-light stuff from OS/OSR-D&D, Traveller, Barbarians of Lemuria, etc., that I could probably just dispense with all my books and use whatever simple d20 or 2d6 mechanics fit the adventure concept.  

That said, to the OP:

I've gone through many cycles of purge down to "only what I need," only to gradually acquire more.  At this moment, if I had to choose 10 or fewer books, my list would be:

Barbarians of Lemuria: Mythic Edition
Everywhen
OD&D LBBs + Greyhawk
Stars Without Number
Night's Black Agents
Fading Suns 2e
Blades in the Dark