This has seen a huge amount of development in games lately. Pathfinder 2E Playtest has just published this blog post about actions and I got to say, 'I love it!'
Pathfinder 2E
Basically, you get 3 actions on your turn. That's it. Done. No sorting them into different categories. You can even take the same action 3 times by the sound of it. :) Some things, like casting most spells take 2 actions, and it sounds like repeating the attack action increases penalties. But, how cool is that?
Savage Worlds
Always had that kind of feel for me. In that you can try as many actions as you want, but the penalties stack up. Pretty free.
D&D 5E
Kinda went that way. On your turn you move (not considered an action) AND take 1 action. What you can do with that action varies significantly, such as being able to attack twice for higher level fighters. Then you get a bonus action IF you have a feature that lets you use it. Mike Mearls has already spoken how he would have done this a little differently now and just put these options on top of other actions (without the need for bonus actions).
Coriolis
Gives you 3 Action Points to spend. Quick actions spend 1, normal 3, slow all 3. Sounds great, and I love it, but it is fiddly AND still requires you to remember what each action is AND people still look for ways to squeeze all APs out. Good thing is it has a defend type option (and it sounds like PF) has that.
Fantasy AGE
Also has a range of options sorted into categories, inc the ability to defend on your turn.
So, is Pathfinder that different? I one very important way. NO CATEGORIES for actions. You can do ANY 3 things. I love it. Other games have other complicated rules and add ons (such as feats/talents/features) that let you mess with this anyway. I am in favour of this style of play… let me expand on some of the systems below…
“It is amazing what you can accomplish if you do not care who gets the credit.” – Harry S. Truman