Minecraft
Ever got down on the ground and played Legos with your kid? Yeah... Like that, but so much more involved. Mining, hunting, building, etc... You take raw materials and combine/cook them into something else. You can then take those new materials/ingredients, and make more intricate machines/objects.
My son is the brains behind the operation, and I'm the brawn... Basically, he comes up with the crazy ideas, and leaves me to do heavy lifting while he runs around collecting materials.
We've got a two-story house complete with bedrooms, crafting table, furnace (cook/change materials), & torches for lighting the interior.
On the roof of the house are trees & a garden which the boy planted, and then the perimeter of the roof is ringed with Jack-O-Lanterns that give off light to help us find our way back to the house @ night. There are also pathways leading out from the house and those are lit by torches.
The Light house & torch pathways were necessary in his mind because his character got turned around, and was caught off-guard when the sun went down... @ night, zombies, creepers, skeletons, & spiders come out and will attack you, so we found a quick way to locate our place & then run back should it start getting dark.
We've made tools, fishing poles, a fishing pier jutting out into the water, a boat, gardens, and a large storage chest just to name a few items.
He's loving the game, and I'm having fun watching him come up with ideas, and then getting excited when he sees them actually shape up.