All 4 of my bikes are equipped with a standard aluminum rear rack and a cargo pack. I'd like to be lighter and less bulky.....but carry....a spare tube, tool(s), pump, lock, rain poncho/jersey, a spare jersey/shirt (especially in the humid season ~May 1 thru Oct 1). I also stash my cell phone, car keys, pocket knife/multi tool, and set of reading glasses. Probably have a couple tiny items in there too. No kitchen sink, but some days it feels like there is one.

For even longer day treks add an extra polar bottle of water because sometimes I am off the beaten path and can't risk dehydration, again, when it is hot and humid outside.

A question for those who do NOT use a rack: What do you normally carry as a minimal load and what kind of ride are you taking?
Just curious. (Maybe fuel for a new thread? "Don't use a rack and don't need one")

Thanks to everyone for their insight, I don't post much, but do read and learn a lot about folders here.