GURPS. It has a little bit of a learning curve and some problems with outdated terminology but it is a great system.
Gurps is hands-down my favorite system, but it’s reputation is so terrible I’ve only once convinced a group of players to play it, and only for one session
Some more freeform systems:
Fate, another great “do all” system with like 2 pages of rules, and mitigation against the dice, you can decide to take a malus now to be able to have a bonus later. Though it’s not combat focused, but that usually means you can develop your encounters more rather than use braindead agressive enemies all the time, and make combat to the death only a last resort.
Hillfolk, more like theater impro framework.
“2 pages of rules” 400-pages FATE rulebook next to me: Am I a joke to you?
