There`s a buncha characters for everyone (I assume), that just haven`t been used to their fullest potential. Here`s, hopefully, alla my choices.
you probably notice that it`s mostly DC and MARVEL. Which once again shows, that they don`t let the creators divide enough attention for every character. And of course, every creator doesn`t wanna give enough attention to many characters.
For other characters I think that deserve time in the spotlight...