Yuen Wo Ping is the obvious one that springs to mind, though I think he has lost some impact through saturation.
I like Jackie Chan. I think that his avoidance of wire work in favour of athleticism makes for a more exciting fight, and his recent work has, if anything, been more inventive than his older stuff. (the 'fight creating a painting' in Around the World in 80 days, and the 'singing in the rain' umbrella fight sequence in Shanghai Knights are both inspired and unique)
I also like Jeff Imada, who has lent his expert input to almost every american made MA action movie in the last 25 years.