KOI

Yes. "KOI" is in the ENABLE word list, accepted by Words With Friends and most open Scrabble apps. It scores 7 points in Scrabble and 7 points in Words With Friends.

In Scrabble, "KOI" is worth 7 points before bonuses. In Words With Friends, it's worth 7 points. Played on a triple-word-score, the Scrabble value becomes 21.

Ornamental domesticated varieties of the common carp (Cyprinus carpio), of Japan and eastern Asia with red-gold or white coloring.

No, "KOI" has no anagrams in the ENABLE dictionary — it's the only word that can be formed from its exact letters.