SOME of the most amazing performance, by all means not all.
Fleetwood Mac, Rhiannon (Live, 1976)
Elton John, Candle In The Wind (Live, 1997)
Carreras, Domingo, Pavarotti, Nessun Dorma (Live, 1994)
Joni Mitchell, A Case of You (Live, 1974)
After Forever, Alone/Heart cover (2000's - not sure when...)
Please, feel free to add your own favorite amazing singing performances!