I love the Messiah... "But who may abide" is my absolute favourite aria of all time. Mozart's Requiem is fab as well.
Purcell's opera "Dido and Aeneas" is also brilliant. It's got a rude nickname which I'm probably not allowed to reveal on this forum (but you can probably guess it! *sniggers*). I was in a school production of it a few years ago, and that's what inspired me to have singing lessons (I'm now grade 5).
Musicals? Brilliant also. I simply adore the duet from Miss Saigon, "I Still Believe"... anyone know it? And "My Man's Gone Now" from Porgy and Bess is heart-wrenching.
Oh, and I like classical, baroque, jazz, folk and 70's R'n'B too. (Modern pop and R'n'B don't really appeal to me, although some of the singers are surprisingly talented.) Plus I love to rock