My favorite so far is the Darksiders 2 collectors edition.

Actually kind of liked the big stupid helmet that came with the Killzone 3 collectors edition, art book was also nice. I would have to go with that.

The Grand Theft Auto IV one. The security deposit box fits perfectly in my desk drawer and I keep loose spare cables in it. The duffel bag is used whenever I go to the gym or go on a weekend trip. The keychain is also in use and the art book was great.

The Halo: Reach journal is pretty boss.

@mosespippy said:

The Grand Theft Auto IV one. The security deposit box fits perfectly in my desk drawer and I keep loose spare cables in it. The duffel bag is used whenever I go to the gym or go on a weekend trip. The keychain is also in use and the art book was great.

I agree, that deposit box and the duffel bag got a lot of use.

Every other extra I've gotten with a Collectors Edition has either been thrown away or just stays in the box. Like that cog you got with Gears of War 3.. it looks pretty but it's entirely pointless.