Lets kick this community off with some of the good stuff. I'll go first:

1. Stars without Number - The first of many Kevin Crawford games I love, it's got excellent mechanics that can be easily extracted from the lore for homebrew purposes, but the lore is still pretty cool too.
2. Godbound - Probably the most absurd-in-scope RPG i've ever run. Turns out that when your players are heroes of steel in a world of glass you can teach them valuable lessons about the unintended consequences of taking the easy way out.
3. Star Wars FFG - Hard to run at first, it still has a certain appeal to me for the way it handles success and failure.
4. Lancer: Crunchy mechs and a strategy layer that's quite fun to play. The non-combat stuff is relatively freeform too which encourages RP.
5. Mutants and Masterminds - Last but not least, M&M comes with some caveats: Superheros are so much fun to make. Sure it takes a couple hours, but conceptualizing and building these characters mechanically is actually a ton of fun (protip: use herolab classic to build, its muuuuuuuch easier) The GM guide has some really solid advice on running hero stories of gold, silver, iron, and four color genres. What's more, the mechanics encourage acting like a comic book hero, so players /want/ to save the civilians even if the bad guy escapes because the game rewards them for it!

I could talk a lot more about these games, but this post is already looking pretty long. Tell me about some of your experiences and favorites!