As far as over the top collector's editions goes Infinity Ward and Activision take the cake with the Prestige Edition of Call of Duty: Modern Warfare 2 (or should we just call it Modern Warfare 2 again, the boxes confuse me). Included in the Prestige Edition are not only the Hardened Edition of the game (sold separately) with an art book, but a pair of fully functioning Night Vision Goggles and a head to place them on.
Now exactly what Infinity Ward and Activision envision their most loyal fans using this Night Vision Goggles for is unclear at the moment, but the gut reaction is that this is something to be applauded. No word on just how limited the Prestige Edition will be, but we expect it to be fairly limited and expensive (way more limited than Halo 3's cat helmet at any rate).
If you fancy watching the unboxing follow this youtube link and have a look at Infinity Ward community manager Robert Bowling as he dissects the innards of the very first Prestige Edition of the production line.