My favourite ever performance was The Smiths performing 'This Charming Man' - not live of course, just playback - but Morrissey with his bunch of flowers & hearing aid looked absolutely ridiculous yet effortlessly cool at the same time!
Closely followed by The Jam with 'Eton Riflles' I think this may have been actually live - I can't quite remember. The Jam were one of the greatest live bands ever.
My favourite that I was actually young enough to see has to be either Oasis performing Roll With It, where Noel & Liam swapped around just to take the mick
or Nirvana performing 'Smells like Teen Spirit' in the style of Morrissey - the cheek!!
Looking back; thank god for TOTP2! I hope that isn't cancelled aswell.