Considered a ‘gold standard’ for indie games and independent computing projects in general is Cave Story.
Above is a fan made trailer for the game.
This entire game from the graphics to the music was written by one person, Daisuke “Pixel” Amaya, during his free time over a five year period. It was released for free in 2004 and has been a cult classic ever since due to its nostalgic feeling and catchy soundtrack.
I find it highly inspiring because he started the project as a college student working on it for fun and was able to make something amazing! Inspired by classic 2D side scrolling games such as Super Metroid, Pixel wrote the game in C++.
It’s amazing to me that one person could create such a huge project all on their own. Rather than being a technological feat itself (especially as it’s been 14 years since its release), I find that the opportunities presented by this game lie in how it means literally anyone could create their own large-scale project like this and share it with the world. It seems daunting but is definitely possible, and I find that very inspiring!
Although an updated version titled Cave Story + is currently for sale on multiple platforms, the original remains free on its website! Find it here if you are looking to try it out yourself.