Along with all the good stuff mentioned above, I carry a photocopy of my vehicle registration to be legal. I might be paranoid, but before I leave my car in long-term parking I remove the actual registration & hang it on the fridge. Just worried that should someone steal/break into the car they'll have all my personal info with a pretty logical assumption that no one will be home for a while.

And no, I don't wear aluminum hats (mostly)