Aluminum Can Roof - Roof an outbuilding with cut-up soda or beer cans. Paint it if you want to hide the fact that it's aluminum, or use the pretty colors of the soda cans in your design. You could also use them as siding, thin armor (maybe steel soup cans are better for armor), cladding for small boxes, etc. The round lids of cat food cans can be bent into corner guards for boxes.
Raised Garden Bed Tunnel - If you put in raised garden beds with a bottom, you could then tunnel under them at your leisure, as long as you can hide the entrance. Maybe a small garden box with rockwool in it could be the door, or have something on wheels you can roll aside.
Pulley Grappling Hook - Both in one. Then you can throw the hook, and pull stuff up there. The strings could get tangled though.
Potted Kudzu - Since it's invasive, you could grow it in pots, indoors, for food.
Backwards Underground Bunker: Find any valley. (that part's optional). Make a bunker that can hold an awful lot of dirt on the roof, and then pile a whole lot of fill dirt on top of it. Make a hill. If the point is the thickness of the dirt to protect you from whatever, and not the stealth of it, you could just bring the mountain to Mohammed's bunker. (so to speak).
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