There is no way in the world there is only one best band. It's just impossible. Of course, music, as any art is completely up to the individual so I suppose all of you could actually have a "best band"... anyways, I'll just list the bands I really really like
Red Hot Chili Peppers (my personal favorite)
Sublime
Nirvana
Pink Floyd
Led Zeppelin
Simon and Garfunkel
Everclear
Green Day (new album)