A kitchen utensil to help with cutting the top of boiled eggs. See: https://www.google.de/search?q=Eierschalensollbruchstellenverursacher&tbm=isch
Egg shell. Nuff said. :-)
May be several things depending on context, but usually it's used in mechanical or electrical engineering as predetermined breaking point for devices, components or whole structures to define where and when things should break when something bad happens. May be a short circuit breaker or especially weak mechanical part of a component or even the part of the river bridge that should break first on stress.
Usually the perpetrator of something. Someone or something that happens to cause something. E.g. "Stauverursacher" may be the person causing a traffic jam.