My kids' (5 & 7) current favorites are "Smooth Criminal" (the Alien Ant Farm version), "Uprising" (Muse), "Moves Like Jagger" (Maroon 5), "500 Miles" (The Proclaimers), and "Gangnam Style" (PSY).
We have music in heavy rotation in the car, and these 5 songs are clearly the most requested.
However, I've just finished burning 20 CDs for my daughter's Year One classmates -- as her little year end holiday treat for them (in lieu of lollies). Since some of the parents have strong feelings against young kids listening to anything with overt sexual references (e.g. "Moves Like Jagger"), I've kept the tunes very G-rated. Retro stuff is very good for this purpose!
A few of the tunes on her summer mix:
* Surfin' USA (The Beach Boys)
* Disco Inferno (The Glee version)
* Walkin' On Sunshine (Katrina & the Waves)
* Twistin' By The Pool (The Dire Straits)
* Vacation (The Go Gos)
* MmmBop (Hanson -- way cooler than Justin Bieber could ever hope to be!)
* What Time Is It (High School Muscial)
* Hot, Hot, Hot (Buster Poindexter)
* Let's Groove (Earth, Wind & Fire)
You get the drift...