Emergent gameplay is a big part of what makes video games unique as a medium. I'd say a good example I've played recently is Death Stranding. One of my favorite games of all time at this point, it really is best and worst described as a walking simulator. Or moreso, a delivery simulator. At its core, you'll take on missions involving the delivery of different amounts and sizes/weights of packages to destinations near and far. Sometimes there are invisible ghosts that want to kill you, sometimes there's visible, inanimate landscape that wants to kill you.
What takes it from 'walking simulator' to 'walking simulator' is the fact that the walking is complex. The smoothness or roughness of terrain can directly influence the stability of your character. Even small rocks can be marginally trickier to traverse than truly flat ground. You may find pavement, dirt, rocky terrain, snow, or deep rivers, which require considerations. You can brace yourself for stability to help, and your movement speed, momentum when changing direction, and whether you're standing or crouching all affect your likelihood to slip or trip. Many items help you to move off the beaten path and find shorter routes, with ladders or climbing rope & anchors allowing the scaling or descent of steep cliffs.
Through experimentation, sliding helplessly down a mountain, and having all your important shit get washed away in a river as you scramble around like an infant, you come to understand your mobility and limitations. Enter: the packages and your hubris. You can accept multiple missions at a time. Some missions require few or relatively light packages. Some ask you to move an amount of goods that ought to be palletized. Through understanding your limitations, and attempting to slap different amounts of cargo on your person, you can possess Icarus and fly as close to the sun as you want.
But, there's more than just your person. You can use floating sci fi wheelbarrows that trail behind you, carrying a large amount of goods, but restricting your ability to use climbing ropes or ladders. You could use a motorcycle, allowing for speedy traversal and some light offroading with small storage on "saddlebags", or even a huge ass truck which affords incredible storage potential, at the cost of a squirrelly and incline averse driving model.
And I haven't even really gotten into all of the equipment or strategies required to handle the "ghosts", whose unique abilities and behavior provide an interesting additional challenge where being caught by one could easily mean the loss of your cargo, or even your life. Even in the big ass truck, you aren't truly safe. The intermittent and locational time-accelerating rainfall means even cargo you haven't dropped or bumped can have its durability rusted away given some time.
Though the game, of course, has a story, it sits alongside a story of the player's experience, limited only by the bravery and recklessness with which you, essentially, don't want to make three trips to the car to bring groceries in, so you load up yourself and two linked floating carriers to carry nearly 1,000 kilograms of cargo, and make a winding, manually waypointed journey through the desolate and oppressive landscape, stopping to deliver parts of your massive load as you come to each post-apocalyptic shelter in your list of deliveries.
Your successes and failures within are unique to the way you chose to plan and execute your trips. Shit, man, I like this game.