In my falcon I carry around:

Glove box:
Pens;
Notebook for milage registration and calculating when to fill up (fuell gauge works erratic);
Sun glases;
Dashcam;
Hand whipies;
Flashlight;
Occasionally a chocolate bar;

Under the front seat:
A 99 piece ratchet tool kit (basically the kit I used to tear the car apart and rebuild it;
An army style folding shovell;

Under the rear seat:
Jack, 2 cross wrenches for wheelnuts, prybar for the dog dishes;
(A bucketload of lost pencils, empty candy wrappers and what else my daughter managed to loose)

In the cargo area:
Washer fluid;
Bottle of lead replacement
Bottle of engine oil;
A nice vintage leather tool chest I got from a garage sale with in it: A spanner set, screw drivers, replacement bulbs, gun gum, metal wire, a set of rear bearings, and seal, set of replacement carb studs, 3 hi viz vests, flashlight (can't have enough of those), 2 magazines that My car featured in;
2 fleece plaids, a soccer ball;
2 folding stools;

In the spare compartmet:
A spare
Bottle of rear oil;
Bottle of tranny oil;
An aluminiumfoldable mattres (great for those roadside repairs)

I'm still contemplating making an extra storage space on the drivers side behind the rear wheel well.

Increadible isn't it, and we actually fit into the car as well!

Why? simple, because I can (and spares such as bearings are not easy to come by here).