I know most will think of fuel powered lawn mowers we see often, but i've seen many examples when people were building lawn mowers without need for electricity or gas. Wheel movements were converted into rotary movement of cuttign blades just with simple gears, i think crafting of such device could be possible using plain metals and wood.
Purpose: mow grass and gain straw, sometimes maybe a random seed or two. Maybe a new curiosity to be found while doing it?
Mowing your lawn would of course require grass to coem in at least 2 states: fully grown and freshly mowed. Maybe after the grass is cut it could transform grassland into the yellow (forgot its name) kind of ground.