The Warrior Monks are enemies fought in Bevelle in Final Fantasy X. The two versions share most statistics, differing only in their Agility. The monk wielding the rifle uses an attack which hits a single person, whereas the one wielding the flamethrower unleashes his upon the entire party.
Warrior monks are first fought in the Tower of Light during Yuna and Seymour's wedding. After the party dispatches them, they are not fought until the High Bridge before the Seymour Natus battle. After that, they are only fought in the Zanarkand Ruins as Fallen Monks.
Both types of Warrior Monks, as well as both types of Fallen Monks, count as two enemies for the purpose of anything that counts kills (such as Karma damage or the Slayer overdrive mode). This is because their weapon is considered a separate (albeit untargetable) enemy.