Villagers with their own offers
With one command you can set your own offers for the villagers, so you don't need any additional mods.
Large parking garage
A large parking garage for decorative cars. Unfortunately, completely useless, because in Minecraft without mods is not possible to get working cars.
River Barrier
A good way to block river mouths where no ship is allowed to enter. The barrier consists of glowstone and stone steps.
