[patal]

Remedy and Funatics developed popular games. Though it's not said what they used "D" for.

Remedy is responsible for Alan Wake and Max Payne, Funatics for Cultures, Zanzarah, among others.

[gozo]

By following the links in the wiki:

Remedy: "integrating D with a typical C/C++ game engine as an extension language for use processing game logic"

Funatics: "D as a replacement for the parts of our infrastructure that use nodejs right now"

[agumonkey]

Pretty big names in their field.