Tricube Tales. It's the easiest game I've run, and strikes a perfect balance between rules lite narrative shenanigans and a traditional roleplaying game. Uses an easy to manage 1-3 pool of d6s, and all the GM has to do is pick a Trait (Agile/Brawny/Crafty) and assign a difficulty to the challenge (most of the time it's 5). Character creation is pretty freeform, with PCs getting Fate aspect-style Perks and Quirks. You can run just about anything in Tricube Tales. It's a real joy.

I'm also big into FIST ULTRA Edition, a game about paranormal mercenaries set during the cold war. Inspired by Metal Gear Solid and Doom Patrol, FIST is based on World of Dungeons, so it's a 2d6 system, sort of like PbtA with only a "defy danger" move. The heart and soul of the game are the 200+ Traits, which are a sort of combination half-class, feat, starting gear, and attribute score adjustment. When you make your mercenary, you get to pick two Traits, and the ensuing combination is always fun.

Lately I read Trophy Gold. Very simple system.

Dread is fairly unique and I had a blast running it

I like to introduce new players to RPGs with Cairn. Bare-bones medieval fantasy RPG.

Shadowdark! Everything I love about 5e, none of the cruft.

I just played Shadowdark and my players and I found it refreshingly simple to play. I did a video about it here:

https://youtu.be/mkJCwfzQkfk

Two I really enjoy are Index Card RPG by Runehammer, d20 done nice and light.

The other is Breathless by Fari Games, it has a free SRD and tons of games for it released under the Breathless Jam https://itch.io/jam/breathless-jam/entries

Lasers and Feelings is so rule-light the rules document is actually a 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.

Ironsworn is one of the lightest systems I enjoy, it's on the crunchy end of PbtA. Lots of moves so you don't have to rely on Defy Danger that much when doing some perilous adventuring. Novel way of handling "clocks" with their own set of moves. And fully support Co-op and solo play which also ads some moves.

Blades in the Dark is lighter but I don't quite make the setting work for me, its awesomeness have yet to click for me. Its mechanics though - chef's kiss.