Don't know if anyone's mentioned this one yet, but my favourite service vehicle of all time has to be Michael Salter's "Car Camel":

http://www.netbug.net/blogmichael/?p=389

I had the privilege of riding in it at Targa last year. Yes, it's a mid-90s Caravan that's been chopped in the middle.

It doesn't need any extra ramps for loading and unloading. The rear end is on air suspension that lowers the whole thing right to the ground. And because space is at a premium inside the cab, Michael decided to go for a design that didn't need a separate reservoir tank; instead, all the welds in the rear section were done airtight, and the hollow frame acts as the reservoir for the air suspension system.

It drives very nicely, and everyone loves it. I remember after we DNF'd (mechanical - a rod bolt decided to go on strike) and our crew came to collect us, the Car and Driver crew who were following Rhys Millen for the event happened by and took a whole bunch of photos. I never found out if any of them made it into the magazine.