ooh...  i love oddly colored cels.  
monochromatic, odd lighting, darlky lit, all 
those.  (Larva, purple?)  i'll also jump at cels 
of bishounen wearing pretty expressions (intense 
is good, or sad), or unusual character designs.  
memorable scenes rank right up there too, but the 
rest of my taste is pure whimsy ^_^;;