Last weekend someone backed their car over that little bunny-ear cactus while attempting to turn their car around in my driveway... I performed some minor surgery on the cactus, removing some of the badly-mangled paddles (which I replanted elsewhere in the garden), propping the flattened-but-intact ones back up. Piled some chunky gravel around the base, and lined up a bunch of bigger rocks along the edge of the driveway; so far it seems to be working, no one tried driving through my garden today...