I'd love to see excel running python under the hood with easy integrations to numpy and matplotlib and all that. There actually are a couple such projects I've been meaning to check out.

In essence, I've spent a lot of my career modeling things in excel. For quick, easily shareable prototypes(to pseudo-technical people), excel is great. But add any real complexity and I rapidly find myself using some UGLY hacks to get the functionality that would be trivial if I could just iterate over the data more explicitly. If I could just click a cell and set the output equal to a python function return value, man would that be a tool. THE tool even. I don't really want to learn VBA or something clunky and not very useful outside of that niche context. I already keep too many programming languages in my head between python, c++, FORTRAN, and some bash scripts.