The keypad to unlock the doors/pop the trunk. No, I don't mean the remote entry thing. Car has a little numeric pad on the driver's door that will unlock/lock the doors or pop the truck with a given key sequence. It sounds stupid, but it's so nice not to have to fish in my pocket for my keys when I just want to grab a pen from my car, or to be able to leave the car running to warm up on a cold morning and still have it locked. Plus, I can never lock my keys in my car because of this.
ZV