Omake, bonus and behind-the-scenes material

I think as far as the DLC age is concerned, it's kind of a crime now not to include some bonus features. It's always annoying to see artbooks and dvds/ blu-rays go up to the hundreds online or at conventions, and in these days of downloadable content it oughtta be encouraged to allow these things to be downloadable if they're not included (or a handy link to them online, that too).

Guitar Hero 1 and 2 did this well. So did the first God Of War collection. And of course, Capcom and their arcade collection re-releases have found a way to make a fortune off of it alone, several times.

Any omake or behind the scenes material you really liked in a game you enjoyed? Whether it's built in or through another medium?

The Insomniac Museums from the Ratchet and Clank series are a good example of this. There's usually a lot of interesting behind-the-scenes information and cut material in them, and usually things to mess around with.

Like the particle and projectile editors in the second game's museum. That was fun.

In addition to that, there's some "developer's commentary" playthroughs on You Tube of the second and third games, with one in progress for the first. It's all really neat.