Dolly
What's so great about a dolly?
Well............................ Basically it would be a kind of vehicle, with only one actual "seat", which would be the driver's.
The dolly would be able to interact with certain existing and future items for the purpose of moving them around.
A barrel loaded with liquid or rocks for instance could be moved with a dolly, or the new chest that is incoming, creating a mobile multi purpose container
Heavy vehicle parts could also possibly be moved with a dolly, and also base-building parts like lumber or metal.
Finally, it would be an obvious function of the dolly to restrain people and tie them up to it, and then you would have the ability to wheel around your new human pet.
In order to escape from the dolly, any cuffs first need to be wiggled out of, and then once hands are free, the dolly restraints can be wiggled out of, but only when the dolly is motionless.
The dolly could also be used as a way of transporting unconscious friendlies...
In short, we absolutely need this kind of shit. Large vehicles are great for long distances but we need things for micromanaging large objects too.
I see the dolly as being a possible first in a line of such interactable objects. Wagons, wheelbarrows, and gurnys would be very similar but the classic dolly is the most versatile of the bunch.
A grocery cart is another great example of the kind of wheeled device that we really need when scavenging for resources. When basebuilding becomes relevant we're going to be very thankful if we get so much as a wheelbarrow.
The limits of the grocery cart though is that it is not as strong as a wheelbarrow or dolly, not as big, and the wheels tend to do very very poorly on anything but ashphalt or cement. I can see shooping carts being common in big cities, and they would be great for using in cities when looting or if you wanted to be that mysterious hobo, but beyond that it offers nothing unique over a simply dolly.
A dolly can carry around a barrel, which can hold just as much as a shopping cart, and the dolly can go more places. I'm not saying that I dislike shopping carts, in fact I have suggested them myself in the past, but for the first of it's class (interactable movable "vehicles", I would much rather have a dolly which could fulfill more purposes, although a wheelbarrow might suffice.