In the U.K., I give the Glaswegians top dollar. I love their accent as rough and course as it is. They can say stuff and pull it off. After staying there for an extended period of time, I actually understood them. I know most people would disagree, but I loved their rough-ass accent.
In the U.S. - well, I get a kick out of Boston (New England accent) and well, NY/NJ accents are fun. Oklahoma: some of the rural areas I was at, it was so cute to hear them. They were so friendly.
Canada: (I'm biased) - but I love my relatives' accent in Nova Scotia/Newfoundland. Very endearing and funny as hell. Northern Ontario, they have an accent that's sort of like an inflection of Ojibway Indian thrown in, I love it.
Other accents, not sure. Having lived in the Philippines, I still find the Filipino spoken English accent, still nice to hear. Their sense of humour is completely mental, and it works in their English.
I do like some of the Caribbean accents. They're cute.
Down Under, well I do like some of the Aussie accents. I love the New Zealanders accents. When my Maori buddy stayed with me, we'd howl with laughter at some of the ways we'd say things to each other.
Anyone who has spoken to me on here, may notice an accent. But I cannot say whether or not it's endearing or nice. Difficult to say. People here in Toronto can tell I'm originally from Atlantic Canada.