客 is one of the most commonly used Japanese kanji, and it also has a lot of special readings in addition to the standard onyomi and kunyomi readings.
ONYOMI 音読み
KUNYOMI 訓読み
キャク kyaku カク kaku
Examples
客人たちはその幸せな夫婦が末永く裕福な人生を送る事を祈った。The guests wished the happy couple a long and prosperous life.父は客人の夕食を準備するのに大いに骨を折った。Father went to a lot of trouble to prepare dinner for our guests.