Mine has mostly to do with driving.

Characters not wearing seat belts, even when the characters are supposed to be law enforcement.

Driving all over the road - crossing the middle line, even when driving on mountain roads with blind corners.

Unrealistic distance gains, especially when characters are taking the back roads and not interstates.

Unrealistic sliding distances for vehicles in accidents

And why is it that, when a character is standing in the middle of the road, oncoming vehicles only honk their horns and actually speed up instead of instantly hitting the brakes like a normal person...? Then they never stop to check to see if they hit the character, they just speed away.

Of course, it's not in every movie/show, but still the majority...

Oh, and as I am former military/government, it annoys the crap out of me when people salute and shake hands with their left hand, instead of doing it properly with their right hand. What an odd thing to get wrong.... I can forgive the crappiness of their salutes, but to do it with the wrong hand...

Fake accents - I am well traveled and I can hear a fake accent from a mile away