Cels that I'll never find and/or never be able to afford:
~ The cel in ep 92 of SMS where Haruka is revealed to be
  a woman / any really nice cel of Haruka period
~ Any good bank cel of the outers of SM 
~ The pan cel of Nuriko with his shirt off in ep 30
~ A nice cel of Mitsukake with Tama
~ Arisugawa Juri from Utena
~ Saitoh's Gatotsu
~ An opening cel from Hyper Police where Sakura is flying
  with Natsuki

Hmmm... my list could be longer, but I think I should stop 
now...
(sighs)