Agree with the folks who opt to call the wrecker, when stranded at side of the road, particularly at night.
If it's anything more serious than changing a flat (and, provided I can get far enough off the road to attempt even that), I'm dialing for my friendly "AAA" wrecker, and planning on drinking the dealer's coffee for a couple of hours.
I stock a chemical A/B/C type fire extinguisher, a $50 "Sam's Club" First Aid kit, a cell phone, and—best emergency tool of all—my "Neverlost" ("Magellan") GPS unit.
A cell phone doesn't help much if you're stranded along I-80 in white-out conditions, somewhere between Snowshoe, PN and the next town. You don't know exactly where you are (distance to next exit), can't see the road signs, and you're taking your life in your hands, if you get out and start walking. Happened to me when I was a college student in the '70s.
I spent four hours shivering in a sweater, inside a 20 degree car ("meat locker") with a dead battery (alternator cratered) and I was just damned lucky that a Good Samaritan trucker (God love 'em) saw my road flares through the driving snow, and decided to stop. Most didn't.
I'd thown my dad's road flares in, earlier that day, as an afterthought.
This GPS unit is amazing, and will locate your vehicle to within ten feet. Push the "locate" button, and it'll give distances from nearest exits, roads, towns, etc. , everything the Highway Patrol needs in order to get to you. It even has a "lady" with a sexy voice, who'll direct your sorry butt to the nearest tavern, hotel/motel, hospital, or airport at the push of a button.
I also carry a "Cobra" CB.
I guess minimal hand tools are a good idea, but complicated roadside mechanical operations in this era of swerving drunks, and roadside "opportunists" are something that this middle-aged traveler is gonna ignore.
An earlier poster suggested a sleeping bag, and that's something I'm going to add to my list, for survival's sake, along with a six quart, canteen of water. Lightweigt, space-age foil blankets will fold up, and all but fit in the glove-box, too. I also carry a multi-purpose, emergency flashlight with highway blinker/beacon, and radio bands.
Happy Trails.