I wholeheartedly second the recommendation for Ever Night*. In terms of fight choreography, it's one of the best that I've seen. Some other dramas that fit the criteria:
Faith: The male lead is a general and the king's bodyguard. Many of the supporting characters are also competent fighters.
Legend of Fuyao*: Most of the characters are competent fighters and there's quite a bit of action. The main downside is that the pacing is uneven and it's fairly long at 66 episodes. However, I personally enjoyed it overall. It may be worth a try.
Princess Agents*: This is a great drama if you want a lot of action. Almost all of the main characters are fighters. However, it can get a bit dark and it ends on a cliffhanger.
Fight For My Way: This is unlike most of the other dramas I mentioned in that it focuses on a former taekwondo fighter who gave up on his dream and as a result feels directionless/purposeless; a decade or so later, he's getting back into taekwondo while his childhood best friend simultaneously pursues her dream of becoming an announcer. This one focuses more on character development and relationships, but it's still a pretty good drama.
[Edit: I just remembered I'm in the K-drama subforum so some of those may not be of interest to you. Whoops. ^_^; I'll leave the Chinese dramas there, though, just in case; they're marked with an asterisk.]
