Once you have the essential adequately covered, it is reasonable to stock up on non-essentials.
What would those be? Anything that you can afford, have space for, and would like to be able have without leaving the house. Fasteners (nails, screws, bolts, nuts, washers) wood, tarps, plastic sheeting, duct tape, actual metal duct tape, super glue, silicone. Nobody wants to go to the store after a storm or a break in. Other stuff, like guitar strings that you would not like to go without if there was a longer range problem where you could get out, or stores were closed, or you were unemployed are a good idea as well.
Guitar strings would not be on my list (no one plays at my house) but things like pencils, notebooks, coloring pencils, books (I have 2nd and 4th graders) are in my house. I also stock things that we normally use when they go on sale, or just buy them in bulk at the best price.
Don't just think end of the world, or major disaster. Think saving money! You could buy more guns with the money you save!