The Golem Planter

Its principle: You give a seed to the Planter Golem, and it locks its task onto that specific crop type.

How it works: It locates a field to cultivate anywhere in the chunk, plants the seed, and harvests it when it's ripe. It then stores the harvest in a chest, replants the seeds to create new crops, and puts any excess seeds in a composter. If it collects bone meal, it uses it on the last crop it planted.

Usefulness: It avoids having to enslave villagers to create an automatic farm and is more efficient in terms of farm size.

For crafting, I'm thinking something like the usual golems, but with a carved pumpkin.