I couldn't tell you which is worth the most, or which is the most rare, but I have a few:
Ys: I and II Complete Japanese PC Edition
Ys: The Oath In Felghana (Japanese PC edition, big box, around 8 or so CD soundtrack)
Batman Arkham Asylum Collector's Edition PS3
Metroid Prime Trilogy
Warcraft 3 Collector's Edition
Every World of Warcraft Collector's Edition
Every Starcraft 2 Collector's Edition
Skyrim Collector's Edition PC
Oblivion Collector's Edition PC
Borderlands 2 Loot Crate edition PC
Yeah, I'm a sucker for Collector's Editions. I imagine those two Ys games would be worth a pretty penny right now. Can't even find them on eBay at the moment.