Flail Mary 

(video games) to risk using a melee attack in order to stay alive. This usually occurs when the player is low on ammunition or is due to reload, The odds of success are low but a successful attempt is often celebrated with a sigh of relief or an exuberant shout of victory.

Gamer one: " Remember that sweet flail Mary I pulled off last night? That totally won us the match."

Gamer Two: " You want a medal to go with that swelling head of yours? Get over yourself you poser."

Flail Mary by Knoxford English Dictionary January 12, 2015

fail mary 

the exact opposite of a hail mary which is a miraculous success. a "fail" mary is the extreme degree of an epic fail. the worst possible type of fail one could ever experience.

Person 1: "Did you see what happened during the last 10 seconds of the game last night?"
Person 2: "Yeah...the receiver jumped for the ball, but missed it completely..I mean..it just went right above his head."
Person 1: "You'd think the quarterback went for the "fail mary" play."

insert laugh here....just saying...

fail mary by AnonymousFailBlogger March 18, 2010