Use a Dried Kelp block as fuel in a furnace.

Dye your bed a different color.

Craft and place a Flower Pot.

Use a saddle to ride a pig, then have the pig get hurt from fall damage while riding it.

Place four Sea Pickles in one block.

Power a Furnace with Lava.

Catch and cook a fish!

Harvest some leather.

Construct a better pickaxe.

Use planks and sticks to make a pickaxe.

Open your inventory.

Discover 17 of 40 biomes.

Use a Portal for the first time.