I was watching High Fidelity today, again, and hence...
All time top 5 item songs* in Tamil, criteria: hot item girl, amazing foot tapping music -
Pon meni urugudhe / Moondram pirai
Adi rakkama kaiya thattu / Thalabathi
Thaka thaya thaya / Uyire
Humma Humma / Bombay
I can't think of any for the fifth spot.
*Item song: A song that is not part of the narration and has a special dancer dancing with the Hero or by herself