i carry my complete toolbag for work in the back: screwdrivers, spanners, hammer and so on, so if i break down, whoever stops to help will most likely have everything he (or she) needs to help get me going again.
my i20 came with a tiny first aid kit, but something leaked and things rusted. if i use anything now, i'd need a tetanus shot.
i also carry an awesome rain jacket, a 1m walking stick (from a garden hoe), i had one cable tie but gave it away, a +-40cm wooden curtain railing next to the driver's seat, a handheld gps for geocaching but could be used for non-geocaching activities like not getting lost, a few brown coins, an empty 5L oil container for petrol, orange scented heavy duty handwash soap and a bottle of soapy water for the window squirty thingie.