On long trips: $50 Craftsman socket set.
Need to put in Volvo: my 5-piece torx set.
Non-tools: windshield fluid, water, Rain-X, rag or two, old serp belt.
[On 850 models -- if it's still there -- you'll find a courtesy minimalist tool set in a black pouch next to the spare tire. It contains a weak open end wrench, a screwdriver handle with phillips/straight and 2 torx ends, and gloves
. Yep, gloves. Not getting on Volvo for that, it's a nice touch. Didn't expect it on something non-German / without a hood ornament. The kit contains some other tools, but I can't remember what they are.]