The phaser rifle was a weapon used by the Federation Starfleet in the alternate reality that followed a temporal event in 2233. This rifle variation of a hand-held phaser was a product of Federation technology that had progressed in a different manner than in the reality that universe originated from.
In 2258, around stardate 1313, the USS Enterprise issued a phaser rifle of this type to Commander Spock for a landing party to the planet Delta Vega. James T. Kirk ordered Spock to hand over the rifle when Kirk set off on foot to try and stop the mad Gary Mitchell. (TOS - IDW comic: "Issue 2")
In 2259, around stardate 2259.55, James T. Kirk used a phaser rifle to try to take out Khan Noonien Singh's Jumpship when it was firing on the Daystrom Conference Room at Starfleet Headquarters. (TOS movie: Star Trek Into Darkness)