I have always found the Romance languages, cliché as it is, to be exceptionally attractive. (Hence my having studied a bunch of them.) There's that nice staccato consonant-vowel-consonant-vowel quality of Spanish or Italian, or the softer, fuzzier sound of French or Portuguese or Catalan or Romanian, but they all have something really appealing about them for me.
I've never even begun to study any of the Indic languages but when I've heard things like Sanskrit mantras, I find them really appealing, and I like the sound of Sanskrit's descendants -- Hindi et al. All those "sh" and "r" sounds just really work well together. "Samsara" and "Kshatriya" and "Dharma" and words like that just appeal to me.
I also find Russian oddly appealing, in a totally different way than other languages, due to its weird combinations of consonants. It may just be that I find Slavic men to be attractive, but there's something sort of sexy about those mouthfuls of sounds that Russian and Polish speakers make.
I find Mandarin Chinese pretty nice, too, but other, fairly similar languages are totally unappealing. Vietnamese and Thai (not related to Chinese, but similar in many ways) sound awful to me. I also just don't like the sound of German very much. And there's nothing appealing to me about, say, Arabic. I'm sure a lot of this is based on preexisting cultural concepts, though. It's not like it's a sheer coincidence that Americans tend to find Italian sounds nicer than Arabic.
What languages sound good or bad to my fellow Mellos?