The line uttered by Mcree when he presses whatever button on your device activates the ult, then the enemy team run for their fucking lives to get to cover before he fires
in its original form "it's fuckingnoon" refers to About 1:30 in the morning when you are too shit faced to know the difference between midnight and noon. The expression could also be used to denote that it is to early to go home and that you desire another drink or five.