Songs you can not include:

Any song that was in GH 1, 2, 3, '80s, or Rock Band.
Metallica's "Enter Sandman".
Nirvana's "Smells Like Teen Spirit".
Led Zeppelin's "Stairway to Heaven".

There are other horrible choices, but we'll just flame you to death.

Bosses you can not include:

Any dead person.
Jason Becker.
Any real guitarist as the final boss.