I seem to always drive old beaters, (cheapness, insurance, worry factor etc...)
If you live in a mild climate, a toyota pickup, with a camper shell and an old futon makes a great combo, reliable and cheap. I also had an old 4runner, which was great until the rear power window quit. Then I was stuck running around in the winter with no window, as you have to open it to drop the tailgate. Bad idea.
I've also used a VW rabbit, VW jetta, Toyota minivan, honda civic coupe, volvo 240 wagon, Nissan Pathfinder, and a ford Aerostar. I think the most important thing you can do is to get an old couch cushion or similar, and use it under the button to keep the neck suspended, and provide some shock absorption. (Don't do this if you put the bass in the front seat....
My pal just got a Honda Fit. He can put his DB, a small drum kit, a guitar and an amp, and 3 people in there, plus it has an aux input for an ipod!

That's got my vote for the best transpo for a gigging musician, and as soon as I can get one for 2k, i'll be on it!