Bill Tabor
EF5
Bob, good list. I carry most of those as well. Depending on where you chase as someone mentioned I also agree with a chain saw. Handy in areas like TN, KY, MS, MO, etc where tornado downs trees and prevents you from traveling down the road. Come along or wench particularly be helpful on mud roads, with trees to wench to. Insect repellant is important. I can remember times I got out to shoot some photos and just being covered up in mosquitos!!!
Forgive me if I'm repeating anything that anyone else already mentioned, but I went through this thread a little faster than I might have.
come-along or winch, flares (keep them in freezer-size Ziplocs), tire chains (for getting out of mud), axe (you never know when you might come across someone trapped in debris and in need of urgent medical help), pipe wrench (for turning off gas lines), wire cutters, 12v plug-in spotlight, flashlight, tp, water, non-perishable food, hygrometer, blankets and pillows, window cleaner and paper towels, a bag of quarters for toll booths, tire pressure gauge, spare fuses, hand cleaner, trash bags, insect repellant
You will find every one of those items, as well as pretty much everything else listed by everyone else, in my little sports coupe while I chase.
Don't forget to install new windshield wipers, and get new tires if you don't have some really good rubber already!