The Nirvana one always cracks me up when he sucks on the mic a bit and with his guitar playing style. If that was me I would probably have started laughing in the middle of it.
Awesome find on the new Muse one, I haven't seen that one before, only the live and kicking and Radio 3 ones. Matt looks like he is having fun, haha.
Here's the Muse at Radio 3 one that I posted somewhere else before. They told him not to cuss and he starts dropping F-Bombs at about 1:30
Here's an old one with Iron Maiden on a German show.
Here's a Radiohead one. Nothing really crazy, just the guitar player playing left handed, I guess.
The Smiths - Morrissey comes out with flowers instead of a mic.
This one is pretty funny. Eels - Novocaine with miniature instruments.