I realize close trips don't really require anything but I seldom leave on any bike without:
2 tire levers
small manual air pump
Rain cover for rack bag
Extra battery for rear flasher
Spare brake cable
Spare shifter cable
15mm box wrench (on bikes I need one)
Yes it requires a pretty good size bag to carry all this junk. Yes it adds weight and no I'd rather have it and the weight than to be without.
I used to not carry cables but I tossed a Dual Drive cable on my Speed TR once. Having a cable on the bike would have been a 10 minute fix. Instead it was a blown ride. Stuff like cables goes in those goofy pockets you'd never use anyway and it doesn't weigh much.
So am I nuts to carry all this or just a Sierra Hotel biker?