RS2 - Lumbridge chicken farm
I remember 4 of my irl friends we started a feather business, killing & selling them. (We were like 7-9 years old)
We pulled about 100K cash together and started merching them. Buying them for very cheap on the spot from the noobs and selling them for a profit outside of Varrock West Bank. We did this for like a month straight and manage to get ourselves trimmed/god armours of our choice. Then we would spend most of our time standing outside varrock castle flexing the gear. Good times