I first noticed this in the ultra-boring Ridley Scott epic Kingdom of Heaven, but you can see it in plenty of movies. If there's a recently-dead person who has an important piece of jewelry, like a necklace that is a family heirloom, or even a simple crucifix, the hero will always rip it off their body dramatically, instead of simply unfastening it. The gesture says, "I need to keep this necklace, and also destroy it. My grandfather would want me to have this, and for it to be completely unwearable."
A variation on this convention comes when the hero is knocked out, hospitalized, or otherwise incapacitated, and a villain rips a necklace off of them. That can be seen in the film Walking Tall, when a casino tough tears off The Rock's Special Forces necklace. In these instances, it is sometimes hard to tell why the villain even wants a necklace like that. If it has jewels in it, fine, but why does a non-Special Forces veteran even want a set of dog tags, especially one with a now-broken chain? The answer is, to let the audience know that he will later be killed, definitely by The Rock, and possibly with a two-by-four.
Of course, upon killing his adversary and retrieving the important personal talisman, the hero will again take it off as violently as possible. And the cycle continues.