Well that also includes annoying. There's certain American and Canadian accents that are so smug that you wish everyone spoke in ciphers - that's just an example by the way.
As for England what could possibly be the ugliest accent - could it be the hideous emotion-free Thames estuary accent that is spreading its cancerous glottal-moronic death-rattle that is the worst, or is it the sub-carribean white trash stroke victim accent that is popular with people who may as well be dead, such is their value to society? Or, really, could it be the good old brummie accent or the 'cuts through plate' scouse accent?
My least favourite is Thames estuary for the record.
go go GO!!!