MTG Arena, the new digital client for the Magic the Gathering trading-card game, uses CLIPS to implement the actual game-rules based on the English text of the cards. Magic cards are written using a very standardized language (look at custom-card communities and discussions around "templating"), but the fact that they've had such success with this approach is incredibly impressive to me.
It also leads to some really funny bugs that arise from grammar ambiguities - things like a card that says "[...] then put them into your hand" and the game losing track of what "them" refers to and putting _all_ the cards into your hand.