Thistles. Covered in spikes, bane of young children playing outside, hated by homeowners who want a perfect yard, and loathed by ranchers who fear the weed will take over the grasslands needed by their cattle. Thistles are also edible, at least in parts.
The problem, of course, is the nasty spines. They completely cover the thick, juicy stalks, and the ruffled edges of each leaf. But if you can get beyond them, the inner core of the stem, and the "mid rib" of the leaf (the light green/whitish part), are both edible, and have a texture very similar to celery. There is one downside: thistles, especially the leaf mid rib, tend to be on the bitter side.
