I know a number of these are not from 2012 but it is the year that I stumbled across them.

When My Train Pulls In - Gary Clark Jr. This song is what a mashup of Hendrix and the Black Keys would sound like.
That's Whats Up - Edward Sharpe and Magnetic Zeros. Nu-hippie but so infectious. The female vocalist, Jade Castrinos, really does a great job.
Heartbeat - Childish Gambino. Troy from Community so this instantly gets a +1. The entire album was fantastic but this track kept standing out the most.
That Old Black Hole - Dr. Dog. Solid rock and roll, you could throw a dart at the tracks of this album and any would be just fine on this list.
Forest Whitiker - Brother Ali. Not a 2012 track but a great great hip hop song. "Depending on the day, and depending on what I ate", love that line.
Love Interrupted - Jack White. For me, I can't create a top music anything list that does not include Jack White.
Feels Like We Only Go Backwards - Tame Impala. Groovy pop music, just started listening to them the past couple of weeks. This song might end up being my favorite of the year.
Allies - MuteMath. Harder melodic rock. Kind of reminds me of Incubus, not exactly in sound, but in the way they use the harder stuff but sound softer.
Hold On - Alabama Shakes. What a voice.
Simona La Romona - Spider Bags. I'm always a sucker for great garage band sounds.
No Love - Death Grips. They kind of sound like a 2010 version of RATM. Rap over punk, hard to listen to the first time, but they really grow on you.
Soul Killing - The Ting Tings. The squeaky door song. Love the creativity