12v Cig Plug - Good for charging phones, GPS, or whatever you might need.
Built in Radio - Well a radio is questionable accessory depending oh what kind of route your on, some routes you just cant enjoy the damn thing.
Fan - Like the post office trucks have, right now i have a portable one, but would rather one be built in. The problem with A/C is its not useful in the front cab cause of opening / closing doors, and in the back would be nice, but you would need a big ass A/C unit.
Personal Effects shelf - Some trucks have more of this some less. But an acual place to put an ice chest, coat hanger, bag cubby. Putting this stuff on the shelf is fine been doing it for years, but it would be nice to have your own space for this stuff to contain it and keep loaders from cluttering it up.
Better seats - Again this depends on the truck you get, but i think the seats should be inspected regularly and updated, would reduce alot of wear on the drivers.
And now for fantasy land.
-Mini Fridge
-A/C unit for the back and front
-Carpet in the back
-Large Florescent Lights for back package compartment
-Radio with speakers front in back
-Door Mid truck
-Racing Seats
-New Springs/Shocks
-Hammock =D