Are there any two letters which do not have a distinction between their pronunciation in any tradition of pronunciation? To ask the inverse, is there at least one tradition of pronunciation for each letter that has it pronounced distinctly from every other letter?
For example, a ches and a chof are not pronounced distinctly in traditional Ashkenazic pronunciation, but in many Sefardi traditions they are.
I am including rafeh/dagesh (dotted and undotted) letters as separate letters.