I have stepped on my note book. The spiral part. The metal bit on the end was pointing up and it went through my heel. OUCH! When I lifted up my foot, my note book was still attached!
I’ve removed it from my heel and I think it’s stopped bleeding now.
I didn’t know a note book could cause pain. Any other dopers discovered seemingly innocent items that caused them pain?
Or maybe I’m just an idiot. 
I have smacked myself in the head with my phone at work more times than I can count. Many a caller has heard, “Ouch. 911, what is your emergency?”
When it comes to stepping on things: Leggos are evil
I’ve also stubbed my toe on quite a few peices of furniyure.
Notebooks are extremely dangerous creatures, armed with dozens of razor sharp pieces of paper. I had one sitting open on the floor once, and walked right by it. SLASH! It reached out and clawed my foot. I had two paper cuts on my toe, and believe me, I had an interesting time explaning how the bloody hell I managed to get paper cuts there. Beware the notebook.
Cat whiskers are extremely painful when stepped on. The base is thick and needle-like, and I’ve had a few shed whiskers enter my foot. The upside is I have a neat little collection of my tabby’s shed whiskers.