I carry a tow rope at all times - along with a fairly extensive bag of other useful goodies.
A white with red cross golf umbrella.
BIG tie wraps, small tie wraps, wire, brake cleaner (cleans all sort of things including hands) 3x 500ml Bottles of fresh water, bottle of soapy water (for if the washer bottle freezes) warning triangle, fire extinguisher, wheel wrench (with extendible handle!), a roll of industrial paper towelling, masking tape, two first aid kits, heavy duty jump leads, dynamo torch, a regular torch (AA multi LED job) a picnic blanket and a 12v - 240v 650 watt invertor.
For winter, I took two sleeping bags, snow socks (fabric alternative to snow chains), candles, flask of hot water, tea, coffee, sugar and hot chocolate, chocolate bars, cereal bars, a pair of hiking boots and socks and a change of clothing, enough woollen hats and gloves for 5 people, Cyalume light sticks, two sets of LED cycle lights, with flashing option, and a P7 LED Lenser torch, 5 litres of spare oil and 5 litres of extra low temp. screenwash (down to -20°C) and two ice scrapers.
On 3rd December we went from Windermere to Garve (north of Inverness) and took 25kgs of rock salt/grit too - which I didn't need once despite all the snow.
When I got to Garve, people we were supposed to meet from Edinburgh had been unable to make it!
I didn't even need to put the snow socks on - I think the extra weight helped!
Take a look!
https://picasaweb.google.com/lakelandfolk/ScotlandForTheBrave