Reuben's Train, given by Spaw above , is a great fretless tune, starting out with a slide on the third note and containing lots of super slides. I agree with Frank Profitt that it just doesn't sound right on a fretted banjo. I use an open D tuning for this tune - aDF#AD. This is the only tune I play using this tuning. I mostly use aDADE to play in D. On my fretless, which has a short scale, I tune the banjo to pitch, but on my fretted banjos I tune gCGCD and capo II.