had the arm not-useable for these things:
Did some digging around pre-surgery, and bought this cordless can opener. Worth every penny, and still using it on the original batteries.
Be advised, use GOOD batteries; generics run down fast, but a set of Duracells has been going since November, small cans and large. It doesn't run quickly, but it gets the lid off.
The second came to me post-surgery, when I could used the arm a little: this chopper. Parents had bought one to try, I saw how it worked while down there for a few days, and they gave me one. Cut, say, an onion into quarters, throw it in, pull the cord a few times, chopped onion; how finely depends on how many times you pull.
I don't have many kitchen gadgets, but- especially what the arthritis does with my hands at times- I wish I'd thought of looking for them a long time ago.