I used to carry a set of 1/2" drive sockets. a couple of screwdrivers, a ball peen hammer, a rubber mallet, a gallon jug of water, a flashlight and a pry bar. I had a couple of cars that required roadside maintenance on the regular. Now, like others have said I carry a cell phone and roadside assistance
A cheap socket set [ 1/4 & 3/8 drive SAE & metric ], screw drivers [ philips & straight blade ], a small assortment of metric combination wrenches and a 4 way lug wrench. My GT is a base model so I have a spare tire. Also carry a flash light and my cell phone. Haven't needed any of them so far.