I'm gonna go with my top two because I switch between them so much I cant choose just one.
1) Indie Rock(and pop and whatever else):
I listen to it for many different reasons. They vary from the dissonant and highly interesting sounds of Pavement, to the endless fluid and surprisingly technical jamming of Dinosaur Jr. The soft vocals and charming main ideas of Death Cab for Cutie and The Postal Service leave me feeling refreshed. The wimsical and psychedelic, yet meticulously structured sound of the Flaming Lips well...
[Wayne Coyne] turns gothy frowns to indie grins, as surely as Yoshimi wins!
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The soft calming tones of Iron & Wine can remind you how freaking good an acoustic guitar can sound. The pure strangeness and reckless experimentation of Sonic Youth and the extremely well designed hooks and strangled vocals of Modest Mouse keep me coming back. If those aren't good reasons to listen to music, I don't know what are.
2) Power/Prog Metal kinda stuff:
I will never get tired of listening to Stratovarius, Masterplan, and Sonata Articta. Ever. I don't care if you think it's watered down pop-metal, it's great. Sweeping epic vocals backed up by ethereal keyboards and grounded by solid guitar and pounding double bass is the way to go. There are most definitely more bands than that, but those (and Children of Bodom, who are basically a ridiculously good power metal band in disguise) are the three seeds on my Pandora station, so they get the mention.