This is a hard one. I like all these characters/actors/actresses. However, I'm picking Giancarlo Esposito.
He was such a great Big Bad. The writers, and his acting, made his character a sympathetic villain. You couldn't help but want to know more about him. Also, I don't know about anyone else, but I couldn't decide who I was rooting for during Breaking Bad's season finale... Gus or Walter? That's how good his character was.
Jason Gann follows close behind though. Wilfred, the show and character, are great. More people should watch it.
Jason O'Mara lost points with me for being in Terrible Nova. I thought he was the second best character on that show though (behind Taylor).
Good actors and actresses, but the only one I consider a "breakout star" is Janey Levy, the rest are fairly established. Jason Gann could be considered a breakout star in the US, but he has played the same roll already in Australia, so this is not a breakout in my eyes. Hmm, what to pick, what to pick...
Well, lets start with the fact that (i think) you're a woman. That might contribute to it. And the small, less poignant fact that she hit's every guy's favorite trait of a girl. And she's amazing. and perfect.
There's a good chance that you are in fact the only person on the planet who does not understand the fascination with Zooey Deschanel. Yes, her sister is also good, but Zooey is just adorable. And I don't throw around the word "adorable" lightly, I only reserve it for special occasions.
I would not consider Zooey Deschanel a breakout star. I already knew she existed before. Anyone remember Elf? Giancarlo had an emmy worthy year. He was perfect. (And I have nothing against her whatsoever)
Zooey Deschanel and Giancarlo Esposito can hardly truly be called "Breakout Stars" (as much as I want to give Esposito SUPER MAD PROPS for his work in "Breaking Bad"). But Janey Levy was unheard of, and is fantastic, thus she gets the win here.
I really wanted to like Zooey Deschanel in New Girl and Kat Dennings in Two Broke Girls but the writing on both shows is just so bland. What was the mater here couldn't afford a good writer or were just afraid of being good.