What is the least common game genre?
the least common game genre refers to min(count(genre_id)); genre refers to genre_name
SELECT T.game_name FROM ( SELECT T2.game_name, COUNT(T2.id) FROM genre AS T1 INNER JOIN game AS T2 ON T1.id = T2.genre_id GROUP BY T2.game_name ORDER BY COUNT(T2.id) ASC LIMIT 1 ) t