i just like anything I can play.... I havn't the experience to specify an actual piece, but probably anything without the continuous monotonous offbeats in most concertband stuff I've played.
I like "Bone Appetit." (Not saying I've ever played this.) It's from an album made by Urbie Green, Bill Watrous, Miles Davis, Steve Turre, and many other great trombonists.
Great song... and a great album. (it's on a CD called Absolute Trombone by Michael Davis available at www.hip-bonemusic.com by the way)
I can't pick a single favorite, but this should inspire you..