I am nowhere near this goal, but I believe each bike should be outfitted with the appropriate tool kit. I have a couple bikes that have no allen bolts at all; these can get by with a dogbone wrench (as long as it's the right one) and tire irons and patch kit. I also have one or two bikes on which there is not a single nut/bolt for which I'd need the dogbone wrench. I really don't like going anywhere without tire irons patch kit and pump.

Wet wipes come in handy, especially if you pick up random crap from the side of the road. Which, come to think of it, I do.

I rather religiously pick up tools I see, regardless what they are. 10 lb sledge hammer head? Into the bag it goes. 1/8" to 1/8" coaxial stereo cable? Into the bag it goes. Very rarely do these things prove utterly useless. The coax cable, in fact, has proved very useful indeed; it's short and strong and holds a knot nicely. On a recent ride I broke a strap off my saddle bag, and the coax cable held it together until I got home.