Oh this list is truly lengthy and in some cases made average songs totally abysmal:
Percy Sledge 'when a man loves a woman' - cue Michael Bolton;
George Michael 'Last Christmas' - cue Wigfield (I think that's her name)
Righteous brothers 'unchained melody' - Robson and Jerome
Blondie 'tide is high' - Atomic Kitten
Bee Gees 'Tragedy' - Steps
Percy Sledge 'when a man loves a woman' - cue Michael Bolton;
George Michael 'Last Christmas' - cue Wigfield (I think that's her name)
Righteous brothers 'unchained melody' - Robson and Jerome
Blondie 'tide is high' - Atomic Kitten
Bee Gees 'Tragedy' - Steps