I always wonder about french accents. Like in half of Switzerland you speak at least 10 widely different Swiss German accents but there doesn't appear to be such a thing for the french half.
It might be due to the strongly centralised languages policies of France and the weight of France relative to the rest of French-speaking countries, I don't know, but basically the only accents that can actually be a bit complicated to understand are those of Québec and Louisiana, which have spent several centuries with basically no communication with France.
There's also Africa but I can't speak about the varieties within Africa though, other than the obvious accent difference between North Africa and Sub-Saharan Africa.
It's not the same scale as Swiss German accents that are sometimes completely unintelligible for German speakers, but I have to admit there have been a few times I've been unable to fully understand someone speaking a thick Swiss French accent