I think this is super cool:
How an accountant created an entire RPG inside an Excel spreadsheet
Throughout a few months ending this past February, Cary Walkin created the perfect solution to this problem: an entire RPG made of a spreadsheet and many macros. The game, called Arena.Xlsm, is a turn-based RPG encompassed entirely in an Excel file. Users can download that and use it to progress through levels, collect items, and battle enemies and bosses with melee and ranged attacks as well as spells.
Which probably explains a lot about my childhood.