For the English language, I have always been partial to a strong Welsh accent myself. A nice bit of the Valleys makes me smile. That or some of the Northern Welsh ones with random pausing in the middle of sentences or where some of the words are more drawn out than other accents. Then again, I love a bit of Cymraeg (Welsh) as well! It reminds me of time that I spent in Wales (although ironically in none of the areas that I have mentioned) and some good memories.
For German I have to say the Badisch, specifically the Oberrhein-Alemannisch, Bodensee-Alemannisch and Südalemannisch accents/dialects. I love that it (I guess like Welsh) sounds melodic and there is a lot of intonation. I still get tripped up by some of the vocabulary differences with Hochdeutsch (Standard German one learns in German classes) but, I guess like Welsh, it brings back happy memories of a place where I lived.
For Spanish I would have to say Andalusian, especially in the Province of Granada in Spain. Some of the “simplified” (I use this term rather hesitantly but some native speakers from other parts of Spain have described it – somewhat derogatorily – as such) pronunciation from Castillian and the difference in vocabulary. Just like the other two in my list, it reminds me of good times spent living there for a span and some amazing culture and architecture.
Judging from the list, what I seem to like are dialects rather than the “standard” versions of the language themselves.