Combat Art or Sport
Defaults: Special.
You can opt to learn most combat skills in nonlethal forms aimed at either exhibition (Combat Art skill) or competition (Combat Sport skill). Combat Art skills emphasize graceful movements and perfect stances. Since these skills still give a default to full-fledged, lethal combat skills (see below), they are a logical choice for Pacifists who want some combat ability.
Combat Sport skills concentrate on speed of movement and nondamaging attacks. A failed skill roll means a foul that might disqualify you from a tournament! You can make an IQ-based roll against Combat Sport to recall basic tournament rules, but to become a qualified judge or referee, learn the relevant Games skill.
Combat Art and Sport skills are DX-based, with the same difficulty level and defaults as the corresponding combat skill. A combat skill, its Art form, and its Sport form default among themselves at -3. For instance, Staff Art and Staff Sport are DX/Average skills that default to DX-5, just like Staff skill. A fighter with Staff at 15 would have default Staff Art and Staff Sport skills of 12, while an athlete with Staff Sport at 15 would have Staff and Staff Art skills at 12 by default.
Martial Arts
In a real fight, martial artists with Combat Art or Sport skills function as if their skill were three levels lower. This is because of the -3 default penalty between Art/Sport skills and combat skills. If a combat skill enjoys special benefits – such as the +3 for a retreat when parrying with Boxing, Judo, Karate, or a fencing skill – these do apply to its Art and Sport forms. When these benefits depend on skill level, though, use the level after the -3 default penalty. For instance, to claim +1 damage for knowing Karate at DX level, a karateka with Karate Sport would need DX+3 level.
The reason why Combat Art skills aren't as effective as combat skills in a real fight isn't always that they "emphasize graceful movements and perfect stances," however. Just as often, these skills teach techniques that look impressive in a staged fight without regard for combat effectiveness or traditional aesthetics! Stunt fighters learn such Combat Art skills to put on an entertaining show for the camera or a live audience.
Even so, stunt fighters are still fighters. They may use combat and Combat Sport skills at the usual penalty (-3). To create an actor who knows nothing about fighting but who can simulate a fight by following directions, take Stage Combat. This gives no default to combat skills. For more on simulated combat, see Faking It.
The distinction between combat, Combat Art, and Combat Sport skills is a realistic one. It doesn't always suit fantastic and cinematic settings. The GM is free to waive the -3 default penalty between these skills and allow martial artists who know one skill to use the other two at the same level. This is suitable for action heroes, who use the same moves to pose and show off (Combat Art), compete in tournaments (Combat Sport), and wipe the floor with the bad guys (combat skills).
See Techniques and Combat Art/Sport Skills and Untrained Fighters for other important rules pertaining to Art/Sport skills.