The little metal pegs on a snow blower or a fuse in a circuit are examples I can think of.
I wanted to say fuse…
Fire sprinkler heads have a little glass vile filled with a glycerin based liquid holding the valve closed. When they heat up beyond a certain point, the liquid expands and bursts the vile, releasing the water from the sprinkler head. Note: only the sprinkler head exposed to the fire will dispense water, not the entire system as seen in movies. Also note: that water has been setting in an iron pipe for probably years and is absolutely disgusting.
Similarly, some commercial kitchens have a fuse-able link, which is a metal link in a chain made of some metal with a low melting point. When there’s a fire this link will melt and cause the roll up door between the kitchen and the rest of the building to slam shut.
After writing this I realize that it doesn’t necessarily answer the spirit of the question. But I guess these parts fail to protect the rest of the building, so maybe it does answer the question.
