Oh this is a fun one!
South African (seuth effricahn?) twang is quite fun and unique, but over time I have found it to be a bit grating. I know South Africa is a huge country with several different languages and I'm sure tons of different regional dialects, so I'm generalizing a bit, apologies to any South Africans on here. EDIT: A google search tells me it is the "White Johannesburg" accent I am most likely thinking of.
Had a coworker from Dumfries a few years back and it genuinely felt as though we were speaking different languages. Could barely understand a word the fucker was saying, and honestly I think he struggled to understand me. Google tells me it is a "Dumfries and Galloway" accent but yeah...that one.
And what's life without humility - many American accents are downright terrible. Boston accent? Disgusting. New York accent? Fuck off, I'd rather jump off a bridge. But a special mention to my own - the Philadelphia accent. A dialect so particularly awful, most people from the area lose it the second they leave. The only genuine examples I could point to would be the shows Mare of Eastown (Kate Winslet nailed it) and, to a lesser extent, The Wire.
Probably will have to duck for cover on this one, but I love the Liverpool accent. Can barely understand a word they're saying, but I worked at a summer camp about a decade back and fell in love with a girl with the thickest, most aggressive scouse accent you could find, so it'll always hold a special place in my heart.