Answer
I try to always take
a) a portable battery charger (fully charged) and a set of jump leads
b) a tyre inflate which can be plugged into your cigarette lighter or portable battery charger
c) a ratchet set
d) a foam tyre filler in case you get two punctures and one spare wheel is not
enough
e) a jack
f) spare fuses
g) some wire to connect any electrical failures
h) a first aid kit and a couple of fire extinguishers (a foam/co2 one and a water one) - water extinguishers are no use on fuel fires
i) apparently the legal requirements in some european countries (not france) are a triangle, a fire extinguisher, a luminous jacket, and a first aid kit; but they are not high on my priorities
j) a packet of aspirin