This certainly qualifies as a perfect Shampoo cel, although I'm sure my hormones have a little bit to do with that opinion (as well as the amount I paid for it on ebay)!
This cel is from a scene about four minutes in to the third season episode "Ryoga's Miracle Cure! Hand Over That Soap." Shampoo finds Akane Tendo at the public baths, and is in the process of boasting to Akane that she will never again be a cat. In the scene, the cel is actually cut off at the level of Shampoo's hair beads, hiding her chest and arm. Now if I could just find the matching Akane cel from the shot, I could die a happy cel collector!