On of these sources is a film: Kung Fu Killer.
In it, an incarcerated martial artist (played by Donnie Yen), sees on the news that a high level martial artist has been killed and intuits that there is a serial killer after a number of martial arts masters. Furthermore, he knows the likely sequence that they'll be attacked and manages to convince the police to release him and aid in capturing him.
This seemingly stellar leap in logic is substantiated later in the film through flashbacks -- he was actually approached by the killer as a visitor in jail and challenged to a duel (threatening his loved one if he doesn't manage to get out and agree to the duel). A nice approach, because while you don't doubt the protagonist's innocence (he was in jail) you do find his motivations and his offer suspicious, and than tension is sustained through the early parts of the film.
The other martial arts duels are also a delight to watch, as the killer takes on masters of different disciplines (master of grappling, master of weapons, master of kicking, etc.) in different locations (on a film set, in an apartment, in the middle of traffic).
I also liked the attempt to mix the "hunt for a serial killer" genre with the "martial arts duel" genre -- and the tensions between the maverick/lone wolf/wandering martial artist archetype with the competent by-the-book police officer. However, as would be expected in a movie titled Kung Fu Killer, the kung fu aspect tended to overshadow the killer aspect.
- hearkens back to the days of the AD&D monk progression, wherein an aspirant to the next level must defeat the master immediately above him/her;
- variety in combat location and combat styles does add to the spice of the combat;
- once-sympathetic antagonists turned irredeemable villains are a great addition to the tension of the storyline -- especially if throughout the storyline you feel that you can reach them, until that last clue shows that they've gone over the edge forever.