I don't know what you've got on there already, but...
If you wanna expand your hip-hop repertoire then I'd recommend Jay-Z, Nas, Kanye, and The Knux. If you're even slightly religious (and even if you're not) then Matisyahu is a pretty good mix of hip-hop and reggae.
If you're like Lo-Fi kinda rock then I recommend The Kills, Black Rebel Motorcycle Club, The Black Keys (more bluesy kinda rock), and you can never go wrong with The White Stripes (seriously, check out 'De Stijl', it's a great album that sounds like it was produced in a studio but was really on a bunch of beat up vintage recording equipment in their living room, this is the album that truly made me a fan of TWS)...
In the Rock genre I would also recommend Eagles of Death Metal (not a death metal band btw...), Cage the Elephant (I know you heard the track they did that was in nearly every commercial for the game Borderlands), The Dead Weather, Modest Mouse, The Strokes (though really 'Is This It', their first album, is their best album by far)
If you like punk then NoFX, Me First and the Gimme Gimmes (all cover songs in punk style by the guys from NoFX), The Mighty Mighty BossTones (Ska-Punk), Social Distortion (they're really far more than just a punk band), Dropkick Murphys (Celtic Punk, if you saw 'The Departed' then you heard their version of the song 'I'm Shipping Up to Boston'), The Distillers (they're not bad), and you really can't go wrong with either The Ramones (classic) or The Clash (another punk band that's far more than just a punk band).
Now a few outside of those that I really couldn't add to those for one reason or another (did that even make sense?)...
Dan Le Sac vs. Scroobius Pip - electronica I suppose, but every AcidModder should at least have the song 'Thou Shalt Always Kill' from Angles (there's a line in it about F00) and the video for 'Look For The Woman' since it actually features a TV F00 modded for them and his face on the TV throughout the video...
Fitz and the Tantrums - old skool style R&B/soul style tunes, really good no matter how 'mainstream' it is/was...
Johnny Cash - The original badass in the music industry... 'nuff said...
The Donnas ':censored:in' - Don't laugh, just listen to it... It's pure Sex, Drugs, and Rock'n'Roll... Pass on their other albums as this is the first one they produced themselves for their own label...
Sons of Elvis 'Glodean' - This is a band from my teenage years when 'grunge' ruled the airwaves, my friends and I used to sneak into bars all over the city to see them play. These guys were a great, but very short-lived band from Cleveland, OH. Glodean was their only major label release (actually their only release that you'll be able to find, 'Mrs. White' is a true rarity and pretty much just a bunch of cuts from Glodean), then John Borland (the lead singer) got into a severely disfiguring car accident and that ended things for them... great album that I still listen to today and still holds up well...
