Z71&Gun
Lil-Rokslider
I use a big (~3'x4') Thule clam shell designed for roof racks. I have it turned sideways in the bed. It fits between the wheel wells just right with enough room to put a 110 cooler against the cab. It's lockable, easy to open and holds a lot of gear. When it's against the cab I can reach it to slide it toward the tailgate. The only downside is that it's not secured to the truck, so theoretically the whole thing could be stolen. One of these days I'll design a security system, but then I won't be able to slide it from the cab to tailgate so easily.
