I keep a lot of Lutron stuff on the van for spares and adds. I usually have a Ra2 main repeater, a couple aux repeaters, keypad and a couple of each dimmer/switch plus some HomeWorks devices.

More importantly now that I'm driving the full size Transit I have room for all my demo stuff. Homeworks demo kit, RA2 demo kit, 3 different shade demos and all my fabric binders for shades, seating and Guilford of Maine fabric. I also have lots of other demo/sample stuff... Fabric track, sample pieces of all the shading top treatments, mirror tv glass, Lutron color chips, screen material, acoustic treatment samples, etc.

i just didn't have room for all this stuff before, but it's invaluable to be able to grab a demo or sample on the fly to show a client or designer.  I also have room to carry all the specialty tools that I used to have to unload and load when I needed them.