I've got to admit, while they're not quite 'Grails' in terms of sheer want-y-ness, Earthrise Skywarp.Thundercracker, the Siege Rainmakers, and ER Runabout are pieces I want quite a lot that are freaking hard to find for not-ridiculous prices.

I've recently decided that I want a reissue G1 Ultra Magnus too, I loved that toy as a kid but never bothered picking one up in Japan. There were a LOT of reissue Magnuses there though, so it's not super-elusive/rare/expensive like a Grail is supposed to be IMO.