Key Tronic was the king of rubber. They were possibly the biggest pushers of rubber dome keyboards. Interestingly, they still exist and are doing well.
Some people consider Key Tronic rubber to be quite superior to other rubber domes. I've found dozens of Key Tronic keyboards over time, but found none of them to be particularly good myself.
Before rubber domes, they made a lot of foam and foil boards, some of which felt very terrible, and way before that, very stiff magnetic reed boards.