3D ART
This skill is worth a mention simply because it is an extremely important ability which is needed in every day work, but is often overlooked because it is hidden in everything else an artist does. But an artist may be great at painting landscapes or drawing character faces, but these abilities suddenly become very restricted if the person doesn't have to ability to also modify and experiment with different variations. Just as an example scenario: an artist has made a portrait image of a character, but is then asked to create different age phases because it fits the storyline of the game. If the artist has no skills in manipulating the image, they are forced to paint a whole new set of images, where as a skilled digital manipulator can use the base image and quickly modify in a convincing way.

Here are some before and after examples.