All of us love electronic gadgets in our cars.  Stereos, DVD players, huge amounts of bass, etc.

But, I'm wondering what everyone thinks is their best "non-electronic" vehicle accessory.  For a while, I used a small "garbage bag" that would hang on the back of the seat, that I could throw bits of paper or whatever I wanted into.  This way, it wouldn't clutter up my car!

What non-electronic car gadgets or accessories are your "must haves?"