Several ideas have come forward about how to make a martial arts system for D20 games that is both accurate and fun to play. On EN World some years ago, a poster mentioned making the styles a single feat with the appropriate prerequisites, leaving it up to the player to describe the more cinematic actions of the character. I like this approach personally. Examples:
Feat: Karate
Prerequisites: Improved Unarmed Strike, Weapon Focus: Unarmed Strike, Power Attack, Proficiency in Staff, Nunchaku, Kama, or Tonfa (stats same as Nunchaku)
Description: You have attained significant skill in a traditional hard style of martial arts. You gain an additional +1 to damage with your unarmed strikes, as well as with one of the weapons listed in the feat prerequisites.
Feat: Muay Thai
Prerequisites: Improved Unarmed Strike, Weapon Focus: Unarmed Strike, Toughness
Description: This martial art style emphasizes powerful strikes, close-quarter combat, and the ability to withstand and endure pain. The body is conditioned to give and take, in a brutal and very effective way. You gain Damage Resistance 2 against unarmed attacks and subdual damage. You also get a +2 to your saving throws against any effects which rely on pain, such as Pain Touch, Symbol of Pain, etc.
Feat: Judo
Prerequisites: Improved Unarmed Strike, Improved Trip, 5 ranks in Tumble, 5 ranks in Escape Artist
Description: This martial art specializes in close-quarter combat, spending less time on striking techniques and more time on pins and grapples, within the effective range of most other martial arts. You gain a +1 to touch attacks and grapple checks, and a +1 competence bonus to opposed Str/Dex checks when Tripping an opponent, or when he/she is attempting to Trip you.
What do you all think of this, and have you any suggestions for which martial arts rules worked best for you (even if non-D20)?