Blizzard CE's are always awesome, since they come with excellent art books, making-of discs, and soundtracks, and other stuff specific to the game.
I really liked Fallout: New Vegas' CE as well, the replica chips and deck of cards are really, really cool, although I wish it had a proper art book instead of the comic.
Bioshock 2's CE is also excellent, and the posters really went above and beyond when I discovered that they have secret messages under blacklight.
Lastly, had I paid full price for the Halo: Reach Legendary Edition, I might not have been so impressed, but for $60, that's one hell of a set. I love CE's that are in-game flavored, with things that enhance the story and seem like something that might otherwise be in the game, so this was really quite cool to me.