This version of Little Drummer Boy is beautiful! I can't believe their voices.
Related question: Does anyone know how you can tell if something has been autotuned? Their voices are so perfect and beautiful, I wonder how real that is. (Edit: Apparently this group, Pentatonix, won The Sing-Off on NBC, so they're probably real.)
Gloria in excelsis Deo is such a beautiful sounding phrase, it makes me wish I knew Latin.
Added bonus! Tonight only! In Excelsis Deo is the title of an episode of West Wing. Here's a video of President Bartlet from it ranting in Latin. (Latin starts at 1:12, but it's really worth watching the whole thing.)
His character was such an intelligent president. Oh how I wish he were real.