Mass farming lets you plant crops in large batches. Also lets you harvest all items of the same type within a set radius (ex. if you hold shift while picking up a rock, all rocks within a few metres will pop up as well).

Roundstonescrollfirstperson lets you scroll your camera one more tick to go into first-person mode. Good for placing tricky build pieces or navigating tight spaces with lots of camera clipping.

These are the two mods I'll never play the game again without.