Screw drivers, something big and hard for hitting stuff, a good lug nut wrench especially if you have aftermarket wheels (I use a large 1/2" broken torque wrench), 10mm is a good socket to have. Also a 10mm wrench. Basically think about what could likely possibly happen to your car that you'd need a tool for, and think what tool you'd need to fix it and carry those with you. Basically any tool I buy goes in my car (no, I don't have very many tools, and some I use I leave at home in case my mom needs em). I just throw them in the back floor board, my car is a rolling tool box.
