ENGLISH! ...Hur-de-hur-de-hurr-hurr...
Nah, I'm just kidding. I can't stand English!
Seriously, though, my favourite is probably Portuguese. I don't understand it when it's spoken, but I enjoy hearing it very much. I favour the Portuguese spoken in Portugal to Brazilian, but I think Brazilian Portuguese is beautiful as well. I can read a fair bit of Portuguese, though.
I'm also fond of a couple of Asian languages. Mandarin is my favourite Chinese language; at this point I can follow a LITTLE bit of Mandarin when I hear it, though reading the characters is a no-no as of yet. Mandarin, like Portuguese, has this 'soft' quality, because it uses a lot of fricatives (sh, h, f, s, etc.) beside its plosives. Cantonese and Spanish are a bit more... harsh. Certainly not unpleasing to the ear, but I personally prefer Mandarin.
I like Japanese, though I can only understand a couple of words and can barely make out any sentences, despite my constant viewing of subbed anime in the original Japanese.
Korean is cool as well.
I've developed an affinity for Indonesian, as part of my quest to learn more about my Indonesian roots, and I've arrived at a point where I can understand most of Indonesian, written as well as spoken (at least, when they're not speaking to fast).
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clarity of thought before rashness of action