I still have have to look at products from Atlas (Crime and Punishment, Dynasties and Demogues, Love and War), Bards and Sages (Sharks!, Spider!, Snakes!), Blue Devil (Poisoncraft) , Betabunny (Predators, Book of Familiars), Dark Quest Games, ST Cooley, and additional products not listed below from Adamant (the Imperial Age line), Bastion/Dragonwing, RPGObjects (anything not listed) and Silverthorne (All Hazards, Minor Magicks, Template Trove series).
That stated, below are my favorites to date :
I. OGL
Mutants and Masterminds (Green Ronin)
True 20 Revised (Green Ronin)
II d20 Modern
Adamant
- Foe Factory
- Hot Pursuit (also listed below under DND)
- Hot Pursuit: On Foot (also listed below under DND)
-Terminal Identity: Uplink
- Thrilling Tales: Omnibus
Dog House/Green Ronin
- Sidewinder Recoiled
EN Publishing
- Elements of Magic: Mythic Earth
Green Ronin
- Psychic's Handbook (also listed below under DND)
RPGObjects
- Blood and Fists
- Blood and Fists: Hong Kong Knights
- Blood and Blades
- Modern High
The Game Mechanics
- Modern Player's Manual
III DND
Adamant
- Fantasy Occupations
- Hot Pursuit
- Hot Pursuit: On Foot
Alderac
- Mercenaries
Avalanche
- Noble Steeds
Bastion
- Torn Asunder
EN Publishing
- Elements of Magic: Revised
- Elements of Magic: Lyceian Arcana
Expeditious Retreat
- Magical Medieval Society:Western Europe
Fantasy Flight Games
- Seafarer's Handbook
Green Ronin
- Advanced Bestiary
- Book of the Righteous
- Book of Fiends (or seperately Armies of the Abyss and Legions of Hell)
- Psychic's Handbook
- Shaman's Handbook
- Witch's Handbook
- Cavalier's Handbook
- Eternal Rome
- Medieval Player's Manual
Human Head
- Redhurst Academy
Malhavoc
- Beyond Countless Doorways
- Book of Iron Might
- Book of Roguish Luck
Mongoose (edit: listed this under FFG)
- Quintessential Monk
Monkey God
- From Stone to Steel
Mystic Eye Games
- Artificer's Handbook
Sean K Reynolds
- Fewer Absolutes ( a free set of web articles. Now, if he would finally get around to finishing it)
- New Argonauts
Second World Simulations
- Master of Arms
Silverthorne
- Book of Templates Revised, Deluxe
Skirmisher
- Experts 3.5
Sword and Sorcery
- Relics and Rituals