first thing I make sure I have is the fire extinguisher, thats my no 1 and on a couple of occasions when i havnt had one ive stopped and bought a few bottles of water! paranoid maybe, but id hate to have a full on fire! i had a close scare once and didnt have anything to put it out with, ended up ripping the screen wash bottle from the front dash out and using that.
I always have a very simple bulb type tester for electrics, nothing fancy, its just one of those screwdriver type with a bit of lead and a small crocadile clip on the other end.
I like to take a lot of spares, sods law when you dont you end up needing them!
In the uk I relied on the AA, here in sweden there isnt a breakdown service as such and so I carry more parts.
dizzy cap, points and condensor, fuses, bulbs, fanbelt, sometimes spare cables,can of petrol
jack, extendable wheel nut bar(much better the the 4 way thingys) screwdrivers, adjustable spanner (dont like em but they have there place and in ya tool kit is the place) spanners and bit of wet and dry or sand paper, cable ties, spark plug, jump leads and tow rope and here in sweden you must have a warning triangle which isnt a bad idea especially when you get an off side flat on a busy road! There is talk of flourecent vests becoming compulsary here in the too!