That's right! Doom3 can now be played on your Nvidia Shield!!! Some amazing programmer out there has designed a "source engine" for Doom 3 so you can play it on your Shield 1 or Shield Tablet device. Basically you download the program from the Google Play store (which is very small) and then you have to copy the game files into the folder the game specifies. Directions on what to do are listed in the Play Store description for the download. Follow this link to grab D34A and start playing https://play.google.com/store/apps/details?id=com.n0n3m4.DIII4A&hl=en
Here is a Youtube video showing what the game looks like running on the Shield.
Here is a video showing how to setup Doom 3 on the Shield.