I'm a fan of having "fluid" rules that expect GM decision making all the time.
Make a system that wants rules, and where those rules actually contribute in a meaningful way, or entirely skip them.
It's been suggested but you want to try Apocalypse World, I think. Here's a rule from AW:
When you do something under fire, or dig in to endure fire, roll +cool. On a 10+ you do it. On a 7-9 you flinch, hesitate or stall - the MC can offer you a worse outcome, a hard bargain or an ugly choice.
Doing something under fire can literally mean being shot at, can mean acting under duress, under time pressure.. so the MC has to decide when this kicks in. And on a 7-9 you have to come up with a 'hard bargain' or 'ugly choice' right there at the table depending on the whats, whys and hows of the described action. It's a game that makes the MC a 'player' - you have to be right there in the scene to run it.
On a failure you might have to end the scene and kick into a new one at the drop of a hat. It's exhilarating to run and the same to play.
(I was running it over Easter and it rocked).