Songs guaranteed to get stuck in my head:
Telephone - Lady Gaga
The Big Bang Theory Theme - Barenaked Ladies
Inspector Gadget Theme (yes, I too fall prey to this)
Roflmao - Oxhorn (oh, I was threatened with a beating at the studio after playing that...)
Whataya Want From Me - Adam Lambert (actually, I reckon about half that album plays on repeat in my head...)
And for a while I used to get the Davy Jones' theme from POTC: DMC stuck in my head quite a bit. Daaa da da da daaa da da, daaa da da da daaa da daaa... DAMNIT!