Jimmy Knepper

Though he doesn't seem to be very well-known, I think Jimmy Knepper was one of the best trombonists in jazz from the 60's to the 80's. He's comfortable in a variety of styles and is very technically accomplished, but he also plays with a certain amout of raw soul that's difficult to quantify.

This is the only video with him I can find on the internet that's of decent quality. It isn't really the best example of his playing:
http://www.youtube.com/watch?v=h73im1yqaco&feature=player_embedded

I know he has some good features on Mingus Ah Um and Oh Yeah! (both Charles Mingus albums) if you're interested. I'd recommend picking up a copy of Ah Um (preferably the edition with the three extra tracks) whether or not you're specifically interested Knepper, in fact. It's considered by many to be one of Mingus' best albums, and it sounds just a touch more polished than some of his others.

http://en.wikipedia.org/wiki/Jimmy_Knepper

http://en.wikipedia.org/wiki/Mingus_Ah_Um

http://www.amazon.com/Mingus-Ah-Um-Charles/dp/B00000I14Z