Game System Recommendations - eviltoast

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.