I can tell you from experience, that it really depends a lot on who finds things like your .30-06 pen, and who the Supervisor at that time is, as to whether you'll get to keep it or not. One of TSA's biggest criticism's was inconsistency between airports. Most people didn't realize that it was really inconsistency between screeners and supervisors.
I have a tie-clip that is shaped like a (two dimensional) Colt revolver. It's a single piece of metal, with some nice detail in the surface, but still a small, less-than-one-inch long piece of metal with a clip on the back. A TSA agent took great interest in it, rotating it so he could "look down the muzzle", only to find, perhaps with great disappointment, that it was, indeed, a single, flat piece of metal. That didn't stop him from unclipping it, and rotating it around in his hands a few times before giving it back. I'm sure he was employee of the month.