Well every automotive forum has a "whatz in ur toolbox" thread and they're all boring because everyone just posts their lists and there isn't much discussion. So don't do that. But let's talk about the kinds of roadside emergencies you anticipate and are prepared for, and how that has shaped the contents of ur toolbox. In my experience, minor tire leaks are extremely common so I carry plugs and a little air compressor in addition to the factory tire changing kit and a full size spare. Since I often tow a trailer and trailer wiring is flakey I have a bunch of stuff to deal with that. Battery and alternator problems being common I carry stuff to deal with those. I need to tweak my tool kit a little but the intent is to have all the tools necessary to replace an alternator on the road. I'm tempted to carry a spare alternator or at least replacement diodes but haven't been. Tool wise the hardest part of an alternator replacement is having something to release the tension on the serpentine belt with. I tend to get stuck in the snow and mud from time to time so I carry a tow strap. I've been stranded by transmission failures with no advance warning but haven't figured out a way to do a roadside transmission swap so that one requires a tow. Another use for the tow strap. Murphy's law being what it is everything tends to go to hell when it's cold and dark so I pack a pair of gloves, an extra coat, a flashlight, and a cyalume stick. I used to think cooling system problems were a big deal and statistically they are but nearly always due to a lack of maintenance. So I'm in the habit of checking and replacing cooling hoses more aggressively then I used to, and I pressure test the cooling system every year or so to find any clamps that no longer seal. With that I don't feel like I have to carry spare hoses and clamps.