It's amazing how these things get around. I was prompted to post it here earlier after I sat on one on my chair at the office. No idea how it ended up there, must have hitched a ride on my pant leg or something. That, or... *looks around* somebody here doesn't like me. :-P
The nastiest prickly plant I've yet encountered. Its primary feature is the little burrs that get stuck in your clothes and the soles of your shoes, with spines that are unbelievably long and sharp. It's a common weed in New Mexico. I'm constantly tracking them in the house by mistake, and later stepping on them in my socks. When the burr has been dead for a while, it turns brown and very hard, resembling a small spiky pebble (or alternately, the miniaturized skull of a frost wyrm).