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Phish.
Here is why....

many bands
every day a different one :)
today The Cure, yesterday Megadeth, day before Radiohead. tomorrow no one knows... maybe Pink Floyd ? or Alice in chains
there are too many. maybe another favorites i don't even know yet

Tough call. So I'll give my top 10 that are tied and in no particular order ...

  • Soundgarden
  • Alice in Chains (with Layne Staley)
  • Ozzy Osbourne (with Randy Rhoads)
  • Pantera
  • QOTSA
  • Wolfgang Amadeus Mozart
  • Frédéric Chopin
  • Antonio Vivaldi
  • Niccolò Paganini
  • Johann Sebastian Bach

And my favorite piece from all is ... "St. Matthew Passion, BWV 244 - Aria: Erbarme dich, mein Gott"

It's hard to pick just one.

Beatles
Queen
Led Zeplin
Deep Purple
ACDC
Guns and Roses
Metallica
Pantera
Tool
Dream-Theater
System of A Down
Disturbed
Nirvana

The list could go on and on and on ...

Edit : Black Sabbath , Ozzy Osbourne, Albatross, RATM, Audioslave, Alice in Chains, Megadeth #RIPNick etc

Sisters of Mercy (old goths never die, they just need less make-up)

It kind of rotates, but if pressed, definitely Pearl Jam. The top 10 (even though you didn't ask) are: The Beatles, The Who, Led Zeppelin, Blur, Elvis Costello and the Attractions, The Strokes, The Beach Boys, Teenage Fanclub and Nada Surf.

Foo Fighters

but to be honest there are a lot of great bands out there to just call one my favorite

Active or in the history?

In the history.

Nirvana or Tool