TP,lighters(matches and flint too),booze,cigs, fuel,canned food, folding knives maybe, ammo, a skill,batteries, books on how to information, maps of areas maybe, basic camping materials such as camping stoves, sleeping bags etc. I would say a can opener and trick your average idiot into buying a useless tool that a knife can do but that's a big if.
A bike pump would be a good trade(has more uses than just pumping air such as finding a abandoned gas station and getting out what little gas is at the bottom of the diesel).
coffee beans or grounds because america is addicted to caffeine. anti-biotics, pain killers, OTC meds. Bleach can be used as a disinfectant(no added smelly stuff only the good original).
Disposable plates are a good trade like you wouldnt believe since most people arent gonna be able to carry done and bulk up with their ceramic plates plus cleaning them. Shampoo, Soap, and Toothpaste
I would say things to avoid is obviously electronics, frozen stuff and other perishables.