"Lay Your Cards Out" by Polica.
LOVE this band. The ethereal quality to her vocals. The vocals themselves. The facts that it's only a singer, a bassist, and two drummers with no lead guitarist. This music video. Plus, I am totally head over heels in love with the lead singer. She is gorgeous and can totally rock a pixie cut.
"Anna Sun" by Walk the Moon
These guys had a fun stage presence. They wore flecks of multicolored facepaint and had a good energy to them.
"July" by Youth Lagoon
They were funny and super nice. Really laidback feel to their performance. Just two guys in ratty flannel shirts jamming on a soundboard and a mini-keyboard. Pretty minimalistic, in a way.
"Stuck in My ID" by Reptar
My brother has been a fan of them for awhile, and after seeing them, I'm disappointed I didn't discover them sooner. These guys seem very low-key but also very strange. Their outfits were either weird or too casual (the keyboardist was up there in gym shorts, a tshirt, sweatbands, and addidas sneakers with mismatched socks). They were by far the best performance I saw during SouthBy. So high energy and their music is addictive. So much fun. The entire venue was dancing.
Check out their new album: http://itunes.apple.com/us/album/body-faucet/id514162106