I just picked up my 600th unique NES game, Legends of the Diamond. The funny thing is that along with all of the uber-rares, there's still a bunch of commons on my missing list.
Did you ever go out hunting and see a common game that you could have sworn that you had because its so common, and then when you got home you find that you still needed it?
One of these days I'm going to have to take a few pictures for the "Room of Doom" section here.