In any film or series where the characters are carrying guns regularly I immediately notice muzzle discipline. If the actors actively keep their weapons pointed away from everyone except enemies, you know they had someone competent on staff who gave them some basic weapon handling training before filming. If the characters are supposed to be professional military or law enforcement and they have bad muzzle discipline it immediately takes me out of the scene. If the character is supposed to be competent but waves their gun around like a moron it's very immersion-breaking.

In very well produced media, the characters who are supposed to be amateurs show bad muzzle discipline and sometimes it's even a plot point, and I appreciate that kind of attention to detail.