My favorite example of (formerly) low-hanging fruit is the formula for determining how often you can fold a piece of paper in half. Is there anyone who didn't grow up "learning" that you can't fold a piece of paper in half more than six or seven times? Until high school student Britney Gallivan found the formula, with basic algebra, and extended the record to twelve folds. [0]
[0] https://en.wikipedia.org/wiki/Britney_Gallivan