Dracula X: Rondo of Blood with original case and booklet - PC Engine
Chrono Trigger with box and booklet - SNES
Mega Man X3 with box - SNES
Super Mario RPG with box and booklet - SNES
Secret of Mana with box and booklet - SNES
Final Fantasy III with box and booklet - SNES
All 6 of the NES Mega Man games complete with boxes and booklets.
Not a video game, but still video game related - the complete collection of Nintendo Power Magazine...EVERY issue: July/August 1988 - June 2008. All of them in very good condition including the issues from the late 80's and early 90's.
I find my Super Game Boy as the gold of my collection because I always play my classic Game Boy games with it. 8)