We're doing 'Adiemus' in my school choir at the moment with the two school bands as well. That's definately my favourite. It's going to be amazing, well over one hundred people singing at the same time. Problem is, only three people are singing the top soprano line, one of whom wpn't sing loudly and the other hasn't turned up to rehearsal for weeks (the third being me.) It's so irritating, I'm having a hard enough time with it as it requires me to basically shout for the whole thing, which basically kills my throat.
We're also singing a two part version of 'We wish you a merry christmas' and 'Carol of the Children.' I like them, but they're no where near as good as 'Adiemus.'