With back-lit arcade buttons being more and more commonplace these days, I feel thereā€™s a lot of potential for themed buttons. These wouldnā€™t be used for the primary play buttons, they are intended for secondary buttons like player select and menu. The ones for Street Fighter above are normal buttons with a teardrop-shaped mount.
I have a few others in mind for Pac-Man and Donkey Kong, may share those down the line.
Unrelated: here are some new posts I buried that you may not have seen. Here are some updated posts.