Some are just too outrageous, like the square dance caller in Giant who turns around and talks to someone behind him and all the time the call is coming out over the speakers and the dancers are still dancing.

And then there are the mandatory climbing through the ventilation duct scenes. There are two things wrong with those, that EVERY movie & TV show gets wrong.
1. The duct outlets in every room are rarely larger than 8 inches and often much smaller.
2.Sections of duct are screwed together with lots of sheet metal screw that have very sharp points, which protrude through on the inside. Even if you were small enough to squeeze through the vent you would certainly get torn to shreds on the screws.

And lets not talk about cutting torches, I've never seen a show where anyone ever really cut a piece of steel. They just wave the flame around a little and the piece falls off, always just in the nick of time of course.

Bert.