My first six have become the cornerstones of d20 fantasy gaming for me. I left D&D and its baggage long before 3E in search of systems that could produce a fantasy gaming experience comparable to what I read in novels and saw in movies. The perfect d20 mix for Modern & Sci-fi gaming is still an elusive holy grail for me, but some of my main building blocks are also listed.
1. Conan RPG, Atlantean Edition - convinced me that d20 could do Swords-n-Sorcery and escape the default D&D style of play. It's become the foundation of all my d20 fantasy gaming.
2. Book of the Righteous - the gold standard of what religious-themed sourcebooks should be.
3. Grim Tales - My construction kit of choice and 2nd "core rulebook" behind Conan.
4. Game of Thrones - Aside from being a wonderful resource on the book, I quickly adopted the rules for Influence, several prestige classes, and some other bits for my campaign. Another great example of a licensed property done right.
5. True Sorcery - the magic system I've been seeking for 20 years. A customizable spell system that allows me to develop a multitude of spells without being slaved to D&D's high-fantasy approach. Having rules for blending with Thieves' World was icing on the cake.
6. Thieves' World Player's Manual - Another licensed setting I have always wanted, this was a first-rate d20 treatment (although I would have preferred OGL). I Conan-ized several of the classes. Thanks to Green Ronin for providing the sorcery style separation (mage, priest, witch) I have been trying to emulate with various systems for years.
7. Spycraft 2.0 - This would have made the list on the basis of Dramatic Conflicts alone. The skills, feats, firearm rules and campaign qualities make the game shine.
8. Mutants & Masterminds 2e - And people said d20 couldn't do superheroes. I'm still blown away at the quality of the game and how well it reproduces comic-style combat.
9. Monsternomicon - The gold standard of monster books. One of the few monster books that is entertaining to sit down and read in addition to being filled with setting flavor/fluff.
10. Fields of Blood - A flexible mass combat system that doesn't slow play. This was the first mass combat system I've ever used where my players enjoyed large-scale battles as much as personal combats.
I have to say, if the list were inclusive of WotC books, very few would make the list. I would give WotC kudos for the d20 license and OGL at #1 but every one of the books I've listed would beat a D&D rulebook. If D&D didn't focus primarily on "fantasy superhero action hour (now with better magic items!)", it would probably be a different story.
Azgulor
(Very) Close runner-ups include the Kingdoms of Kalamar Campaign Setting, A Magical Medievel Society: Western Europe, and the Iron Kingdoms Character's Guide.
. Places 5 and 6 and the places 7 to 10 shared the same number of votes, respectively.
