Slayers has some of the single most inspiring TTRPG design I've ever seen. Combat is asymmetrical in that each class behaves and plays in completely unique ways. They aren't "balanced" in a traditional sense, but they play well together and that's way more important. It has a decent amount of crunch, while still being rules-lite enough that really the entire fucking world is open and that's honestly sick as hell.
This game is a D&D Killer in every sense of the word, it's some of the strongest design you'll ever come across in the indie space.
Outside of this, Slayers has one of the strongest SRD's, and Open Licenses you'll find, which means everyone can make (and is encouraged to make) Slayers content. So there is a huge group of 3rd party Slayers content. Unlike another D&D you don't owe Spencer your money for using the Open License, which means there is a bustling group of third party content you can find here.
I know what you're here thinking though:
"You know, this game looks good, but I wish it was set in the wild west instead"
And like hold onto your fucking boots partner because I'm about to rock your goddamn world
Dust is an official supplement for Slayers that drops a desert into the middle of the setting, adds a new class (The Deadeye, a Rifle wielding motherfucker), a ton of new high quality content/maps/art, and 4 new Wild West Adventures, including of course a train robbery
Side note I love a train robbery
Anyway, Slayers is well worth the money, and if you've made it this far into this post without going up to get it what's wrong with you it's so good go get it.