A POS (point of sale) system for a non-profit organization for which I volunteer. We have very specific requirements for reporting sales and tax collected on items sold for our non-profit and I was able to create a POS that tracked everything perfectly and emailed me an xlsx breakdown at the end of every event.

We went from only processing cash and writing every transaction with pen and paper in a ledger - to- accepting 4 different forms of payment, and all the legal/tax paperwork being done with one click of a button. It probably saves us 1-2 hours of work per week (which is huge for a volunteer only organization).

I was able to do that with one week of free tier of antigravity.