Coffee, tobacco, refillable lighters; matches; medicines; medical supplies; soap and sanitary goods. A person with a reliable means to provide electric for rehanging things could depending on the event barter as well as being able to make large volumes of clean safe drinking water would be another barter item. A long down the road barter item would if you have a good stable long term power set-up might be 3D printers. The ability to make spare parts would certainly become a way to make a living in a long term grid down situation.
These threads always seem to never mention hand tools. hammers, saws, ax, shovels, hoes, etc. Files to sharpen. Nails, screws all the things that are needed to build, repair or even just do a small garden.