But this is all beside the point. I take some things with me now. My tool kit, patch kit and tire pump, basically, and a spare inner tube. It's like that tangle of stuff in most people's trunks, where they keep the bottle of wiper fluid, the scraper, the bungee cords and jumper cables. It comes in handy: a few days ago I realized that the screws had loosened that held my tail light up, and it was drooping into my rack, blocking out the light. I dug out the toolkit and straightened it out, in the slush and rain, and was pleased that just this once, I had the tools when I wanted them, and so wasn't stuck bending a key on my keyring trying to make it work as an improvised screwdriver.
And the other day I realized that I really ought to have bungee cords. My parents sent me a package from New Brunswick on the bus (thanks, by the way, guys! And the cookies were a nice touch.) So I had to ride over to the bus station to pick it up. My panniers are pretty huge, but the citrus box they sent turned out not to fit. Luckily, I have a rack! And the box, before being taped, had been tied shut with twine. And, after a bit of possibly dodgy gingeing, involving threading the cable lock through the twine at the back and then up around my seatpost, and then clipping the closures on the panniers through the twine on the sides, I got something that actually did not shift in flight (a good thing, because a snowy South Bank Street is not somewhere you want the unexpected to happen.)
I know that cargo isn't really such a tricky thing, but I was pretty pleased with what I managed to do with what I happened to have on me. Still, I think now it might be useful to carry some bungees around in that bottom-of-the-bag space full of stuff you only ever need sometimes. Cause when that 'sometimes' rolls around, and you actually do have the stuff you need, man, do you ever feel smug.