My personal favorite is NWA (when I was in Syracuse, NW was the only carrier with nonstop DTW-SYR flights). They've been reasonably competent at most everything (luggage service at DTW being the only major exception)
However, United has started to creep up my list for 2 reasons. 1) they have in-flight audio, including "Channel 9" (flight deck radio, which I, being a geek, find extremely cool), and 2) they keep bumping me and giving me free flights, so I'm going to keep flying with them.