I don't know if counts as slutty, but my favorite is Crazy 4 U. The PV's dance scene gives me life! She looks so sexy and cool. SHAKE IT is also one of my favorites, I remember that google used to have an image of Kumi doing the SHAKE IT performance at First Class Live as one of the first images that pop up when you searched her name, and I was so into that, trying to find where was that. haha
One of the best versions of Ima sugu hoshii is that "cassino" remix for the Second Session Tour, it's soooo great, and the performance is so fun with the fan going crazy. I wish we could have the studio version (it actually has one, on the making of we got a little part of the song).