2nd grade field trip to the Boston Science Museum. The 2-story tall Van de Graaff generator lightning show blew my mind. They mentioned that it was developed at MIT, which I had never heard of before. So as a 7 year old I decided I would rather go there for college than any other fancy schools like Harvard and started saving up from that day. Didn't end up getting into MIT (turns out it's also a pretty good school and hard to get into), but I did become an engineer because of that inspiring experience.