Watch for loose car stereos
One of our department's two-officer units stopped a vehicle for reckless driving/DUI. While searching the vehicle incident to the driver's arrest, one of the officers noticed a piece of tissue shoved in a space between the car stereo and the dash cutout, which seemed out of the ordinary. When he pulled on the stereo, it slid right out of the dash. Behind it he found hidden golf ball-sized baggies of Crystal Meth. Needless to say, when I'm searching a vehicle I always check to see if the car stereo is loose.