This is just off the top of my head: (and none of these are "game changers")
Stone of Jordan
Crit Mempo (have had two, both rolled Magic Find)
Leorics ring (farmed for it many many hours!)
Legendary Plans for anything of any type... (do they even exist?)
i know there are more, but even for the items that do drop, you don't see any on a single one of my toons.
if i wanted to play a specific build as a monk for example, Tempest Rush, i personally would never have been able to without the use of the AH.
this is not a rant or anti RoS anything or "keep the AH", but in light of the recent topics here in general discussion, i really do hope that when RoS does go live and we're stuck with what drops, i hope that we're not stuck without the ability to try new or exciting builds because you never get the drop that allows it.
how about you guys, anything you've never seen drop personally and always wish had?