"Hate to Say I Told You So" - The Hives
After I first heard this song, I had it stuck in my head for about two weeks, humming it incessantly. I finally managed to get it out by listening to it again about five times in a row. While the amazingly-catchy riff is awesome, the best thing about the song is that part in the video when the bassist plays alone: the rest of the band is frozen in time and it's just him, his moustache, his bass and a look of grim determination left. If I ever take up the bass I'm going to have to wear a moustache like his.
Wolfmother - Joker and the Thief.