Unlockable: Tool Upgrades

Golden Axe - Throw an axe into the town fountain to randomly turn it golden.
Golden Fishing Rod - Catch every species of fish.
Golden Net - Catch every species of insect.
Golden Shovel - Bury a normal shovel, then dig it up a full day later.
Golden Slingshot - Knock down eight balloons to have a random chance of obtaining it from a balloon.
Golden Watering Can - Earn a "Perfect" town rating for fifteen days, then talk to Pelly at Town Hall.
Silver Axe - Throw an axe into the town fountain.
Silver Fishing Rod - Purchase from Tom Nook's store.
Silver Net - Purchase from Tom Nook's store.
Silver Shovel - Obtain from Resetti's Surveillance Center in the city.
Silver Slingshot - Purchase from Tom Nook's store.
Silver Watering Can - Purchase fifty bags of seeds from Tom Nook's store.