Who are some good musical artists that I should download in iTunes?

I know I'm forgetting some really good artists, but there's so many I just can't put my finger on who I'm forgetting. I listen to a bit of everything. Here's an idea of what's in my iTunes already: Lifehouse, Arcade Fire, Deathcab for Cutie, Maroon 5, James Blunt, Jimmy Buffett, Quietdrive, City and Colour, Cream, Deftones, Pixies, Depeche Mode, Foo Fighters, Goo Goo Dolls, Grand Funk Railroad, Green Day, Mos Def, New Pornographers, Ludo, Lykke Li, Coldplay, Weezer, The Smiths, Dashboard Confessional, et cetera.