Supermassive Black H*** by Muse hands down. I've created a ring tone with it for my iphone.
However, I really do like the Paramore songs, especially Decode and I really like the Mute Math song. I also like Tremble for my Beloved song, Eyes on Fire, and Full Moon.
I don't like the prom song at all - ugh! And I don't like the Perry Ferrell song - really cheesy.
That IS hard. I really liked "Decode" by Paramore and "Supermassive Black H***" by Muse!
The soundtrack was REALLY good but those were my favorites!