Here are a few (of the "not-so-obvious") things I take along:
Spare batteries and vid tapes/film for everything
DeLorme maps + GPS
Cellphone w/NWSFO (and nowcaster) #'s on speed-dial
Maps (I created) pointing the way to almost every library in The Alley
List of dial-up #'s for my provider for almost every town in The Alley
BRAND NEW tires and windshield wipers on the vehicle every March
Bright yellow jacket for standing roadside in adverse conditions (I certainly want to be seen by passing traffic!)
Come-along (winch-type thingy) and tow ropes, snow ("mud") chains, flares kept in Ziploc bags, first-aid kit, duct tape, plastic sheeting (in case of window loss), tp, water, non-perishable food, gloves, "fix-a-flat", binoculars (though I've yet to actually use them), hygrometer, wx radio, walkie-talkies, blankets and pillows, tripod (the heavier the better...they will be in strong inflow), ruler (measure hail), window-cleaner, paper towels, installation discs for such laptop software as GPS, (re-chargeable) battery charger, quarters for toll booths, spare cable for laptop-to-modem connection
Bob