Favorite choral pieces evar?

[igasu]

Not that you guys read and/ or respond to my posts (although I know some of you do and I appreciate it!), but I am working on a repertoire finding assignment, and my question is this:

What are some of your favorite choral pieces of all time and why?

If your reasoning seems logical, I will probably add it to my library and program it for my relatively soon to be choir! (once I graduate and get a job :p)

Thanks in advance!! :)