Nothing jumps out straight away so I'm going to scan my reviews and mention a few that I really liked.
Elebits has a great soundtrack and "The Smile of You" is a great way to lead it. A good singer in the Japanese version, nice bouncy accompaniment, and lots of lush electronic sounds like the instrumental tracks. The single is great as it contains many instrumental tracks as well.
A recent one I came to like was Haunting Ground's Endless Zero. As I said in my review, cold, fragmented, and sometimes whispering vocals appear against surreal, aseptic, perhaps industrial-inspired beats. It's difficult to provide a description to do it justice as there is probably nothing out there quite like it.
I like all the vocal themes in the original Disgaea. I think my favourite is "Etna Boogie". Even I find the vocals hot in that one. The vocals in the sequels weren't so good and I didn't like many of Disgaea 3's at all.
Monster Hunter 2 has a cool ethnic-inspired vocal theme. It was nicely remixed Norihiko Hibino who often writes awesome vocal themes. If it counts, No More Heroes Dark Side's "PURE-WHITE GIANT TINY GLASTONBURY" has to be one of my favourite tunes ever too. Also Romancing SaGa's Passionate Rhythm and Minuet are just fantastic.