I don't know if there are any obvious "visible to the naked eye" low-hanging fruit left, but CRISPR was very much this kind of thing: A group of researchers, investigating a known phenomenon of repeating genetic features of bacteria resisting to viral attack. In one case, all because a group of researchers were trying to make more resistant cultures for yoghurt production.<br><br>I can't speak for disciplines outside my own (microbiology) but I'd wager there's tons of stuff like that out there still, and it's all a fantastic argument to just let specialists do basic research without an eye to practicality, because those kinds of big, basic questions are how we get the biggest and grandest results.