We make a gadget that's powered by a 12 volt wart, and sometimes a user applies 24 and blows one up.
We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS. It's posssible that most any useful polyfuse+TVS combo can be teased to destruction.
I think Phil H mentioned some gadget, a polyzorb or something, that would be better. I can't find it.
We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR crowbar, or something.
This is all entangled with parts availabity. Ideally the box would just work from 12 or 24, but that has separate complications.
We once used a TI electronic fuse IC, but it liked to blow up.