please help ID this plant o' pain

This beast volunteered in some composted cow & horse manure. It sure wouldn't be fun to step on barefooted. The pointed parts are about the size of a golf ball.  

jimsonweed/one of the daturas

Yes, jimsonweed. One of my favorite weeds. I'll never forget this old description from when some British troops sampled some in salad from Bacon's Rebellion:

The James-Town Weed (which resembles the Thorny Apple of Peru, and I take to be the plant so call’d) is supposed to be one of the greatest coolers in the world. This being an early plant, was gather’d very young for a boil’d salad, by some of the soldiers sent thither to quell the rebellion of Bacon (1676); and some of them ate plentifully of it, the effect of which was a very pleasant comedy, for they turned natural fools upon it for several days: one would blow up a feather in the air; another would dart straws at it with much fury; and another, stark naked, was sitting up in a corner like a monkey, grinning and making mows [grimaces] at them; a fourth would fondly kiss and paw his companions, and sneer in their faces with a countenance more antic than any in a Dutch droll [comedy].

In this frantic condition they were confined, lest they should, in their folly, destroy themselves— though it was observed that all their actions were full of innocence and good nature. Indeed, they were not very cleanly; for they would have wallowed in their own excrements, if they had not been prevented. A thousand such simple tricks they played, and after eleven days returned themselves again, not remembering anything that had passed.

Don't eat it!

Yikes. Jimsonweed. Sure won't be eating any. Thanks for the info. Is it related to poke? That's what I thought it was at first. The plants looks similar.

you must have missed the flowers! they do have fairly big broad leaves like poke, but they have big trumpet-like flowers. they’re in the nightshade family.

Poke will often grow in similar places, but tends to prefer edges of dirt piles, woods, etc. while jimsonweed will more often be seen growing individually out in the open. Jimsonweed is one of those "disturbed ground" plants. The seeds will remain viable for 20 years or more, I think, just waiting for the chance to be brought to the surface to grow. Poke is fleshier and stockier with rounded leaf edges, while jimsonweed is tougher with pointy leaf edges. Poke has a huge, bulbous root when mature, jimson weed does not. Jimsonweed will have a strong, bad odor when cut. Jimsonweed can tolerate drier areas than poke. They are both toxic, with the nod going to jimsonweed--it can be deadly (especially the seeds). Even handling the seeds can supposedly poison, though I've handled them since a kid and never noticed any effect. Every few years you seem to hear of some people who hear you can get high on it dying from smoking it. Like many nightshades, its toxic, interrupting effects on the nervous system can actually be used to treat some neurological disorders (in the proper dosage). Poke can also have some benefits against cancer. I've read of a tradition in the Ozarks of eating one berry a year to help protect against it. Cool weeds!