I have a can of tire sealant and a 12V compressor with pressure gauge. I also have a can of gasoline (cars run of fuel in a traffic on occassion and there a fine for running out of fuel on the autobahn), one refill of washing fluid, a pump spray with concentrated washing fluid (helps to deice the windshield and clean mirrors in a pinch) and some motor oil. As I drive a station wagon, I also have a net and some straps for securing cargo.
I also pack anti fog sponges to clear the windows from the inside and a couple of ice scrapers.
High vis vests, warning triangle and first aid kit are required anyway. I have a vest for every passenger plus a few spares in my trunk.
I also have an unhooking mat. It is handy when some tasks need to be performed in kneeling or prone position. It´s comfortable when changing shoes or boots too.