Some examples (Not Japanese):
ComputerCraft: adds programmable computers in Lua. With in game applications; programmable robots called turtles.
Botania and Thaumcraft are two magical mods with stunning visuals.
Buildcraft and AE2 are logistics-oriented mods.
All in all, vanilla Minecraft is definitely unplayable once you try it with mods.
Edit: Probably worth mentioning that Mojang hired the guy who created the modding API. (See SquareWheel's comment below for correction/details)
Edit: Just finished reading the article (I check the comments first). They mentioned the Redstone logic. Probably worth mentioning as well that a 16-year-old built a scientific calculator using Redstone. https://youtu.be/wgJfVRhotlQ