I have one of these jar openers that used to be my Grama's, but a quick google search and I found they still make them and sell them on Amazon! It's the best. It's adjustable for all kinds of jar lid sizes and give you great mechanical advantage! I even used this once to shut off the water shutoff valve on our hot water heater when it was spewing water everywhere one morning and my hubby was gone on a fishing trip AND took all my tools with him.
My Granny taught me to tap around the edge of a jar with a spoon to open it. EVERYONE on my family makes fun of me for it, but I swear it works.
I was messing around with Tap A Talk and I think I deleted my answer. I have those little rubber thingies all over the house. I buy mine at the Dollar Tree - I think they come in packages of 3 and I love the red ones. I even have one in my car.