I've noticed some vocalists will have at least one song where their singing is rather different from what they usually do. Sometimes it's much better or different sounding from how they usually sing. Here's some I've noticed.

Black Sabbath's "The Writ" - Ozzy probably did the best singing he ever did on this song. It's an amazing vocal performance by him.

Samael's "Inch'allah" - The fact that Vorph actually "sings" on this song is something notable, but his voice is noticeably higher than he usually sings in.

Rammstein's "B********" - Till is almost death growling at one point in the song. He's known for deep singing, but wow.

Death's cover of "Painkiller" - If you heard this song and how Chuck normally sang, you'd notice. It's even a bit of a change from that album, which has a fairly drastic vocal change in general from his usual style.

So anymore anybody here can think of?

I remember when I first heard Led Zeppelin's "The Battle Of Evermore" featuring Sandy Denny of Fairport Convention (some old folk band) . Somewhere in the middle of the song both singers suddenly sing very high for like 10 seconds and that just gave me goosebumps. It's not really a very loud Zep song, rather quiet. The only instrument is, instead of an acoustic guitar, something that sounds like a mandoline...