If it's a PbtA please expand on your system of choice!
I'll start:
I really enjoyed Sexy Battle Wizards, but I think The Witch is Dead speaks to me more. I like player characters just being little weak dudes and struggling against normal stuff. (both of these are free by grant howitt and 1 page of rules)
I also enjoyed rude detectives, it has a surprisingly juicy dice system for a game that's just 4-5 pages. It's themed around child detective stories.
PbtA I like magpies stuff, like avatar and root, but my favorite until now was Fellowship 2e I think. Just so extremely versatile, and it's a joy to give a lot of narrative control to players.
Last one is kinda cheating: my current favorite game is rules light within it's genre. 13th Age is the easiest 'dnd' I've ever seen, and the amount of dumb rules and bookkeeping it prunes has reinvigorated 20f games for me! But compared to other games, it's still a bunch of rules of course.
Lasers and Feelings is so rule-light the rules document is actuallya single page. I played it once and had a blast with my character, who I named Beef McLargeHuge and who got into some weird situations, and mostly solved problems by seducing whoever whatever was convenient.
It's my go to system for a quick one shot to introduce people to ttrpgs. Always fun, crazy, and simple to learn. And minimal work for the DM so long as you're willing to bounce off whatever your players come up with.
I've run some one shots for more experienced players that have been really memorable and full of creative play, too. The simple mechanics don't hold it back. It excels when you're willing to "yes, and" pretty much everything.
There are no DCs. Each player chooses a number between 2 and 5 to represent their characters' aptitudes. High means they're better at Lasers "(technology; science; cold rationality; calm, precise action)", and low means they're better at Feelings "(intuition; diplomacy; seduction; wild, passionate action)". The GM only needs to decide which of those two any action is (they need to roll under their number to succeed at Lasers, and over their number to succeed at Feelings), and also whether the character is prepared (based on the situation), or an expert at the subject (based on their characters' chosen expertise), and for each one they get an extra die. The target number is always the player characters' own chosen number.