One of mine would be Pharangese w hair blowing in 
wind from Arislan.  When I saw that scene, I knew 
I definitely wanted a piece of it.  Couple of 
years later, I found 2 cels from that scene.  I 
eventually let 1 go, but still have the other.

Another cel like that I am still looking for 
would be a pan cel of Kagome & her mother from 
InuYasha - I don't collect Kagome much but that 
one immediately struck a cord with me.