Straight: The Mooks can't hit the hero even when he's standing out in the open, shooting down their comrades.
Mooks can't even hit a single trooper among an army of characters fighting on the heroes' side.
A mook fires upon the hero at point-blank range, and misses outright.
Downplayed: The heroes do get shot by mooks. The shots are never fatal, but may come dangerously close.
Any mook with good aim is swiftly promoted.
The Big Bad conscripts peace-loving peasants to work as his foot soldiers, and they struggle with the world of battle. They miss all the time because they have never seen a gun until they were drafted.
There's a substantial difference between firing a gun on a range and firing a gun in battle, and the stress of combat causes accuracy to suffer.
The standard issue guns are poorly made, inaccurate pieces of garbage.
The mooks are really rooting for the hero, and don't want to hit him.
Exploited: The hero just walks past the mooks completely unprotected, trusting the bad aim of the enemy to protect her/him. It works.
Defied: The mooks' trainer says "Just because you are lowly foot soldiers does not give you the excuse to misfire like a little old lady!"
Discussed: "Don't worry about the foot soldiers. They're the worst shots in the multiverse."
Conversed: "Why doesn't the bad guy ever teach his goons to aim correctly?"
Deconstructed: The mooks are such terrible shots that the Big Bad is always shooting them for letting the hero get past them.
Reconstructed: This behavior breeds a deep resentment within the mooks, and leads them to realize that the hero was right all along. Thus, they begin missing on purpose, en masse, because their boss can't just shoot them all.
The bad guys couldn't hit the broad side of the main trope if they had all day.