I thought it might be nice to set up a thread in which we can recommend game systems to one another. What do you like? Why? Give us a quick blurb about a game you like and why you think others might like it. Maybe call out if you think it would be good for absolute beginners or folks new to the OSR/NSR. Oh and the genre too. If this gains some steam, I’ll pin it to the sidebar for easy access.
Recommending some free game systems of some different flavors - because free is best for people who are interested in exploring OSR.
Worlds without Number (and other games from Kevin Crawford). Great free version with basically the whole rule system and some great generators. Has a bit more character creation crunch than other systems so it can be a good transition from 5e
Basic Fantasy Rpg. Retro clone with some 'modern niceties' like ascending armour class. All the rules, supplements and some great adventures are available free on their website.
Mausritter. Rules light (into the odd based) system with a pay what you want version. DnD broken down to it's simplest core where you play as cute mice adventurers.