Paint Sprayer

Paint on its own is a per tile chore. You place the block, swap to a brush, then click the same spot again. With the sprayer in your bags every block, wall and piece of furniture comes out of your hand already colored, which removes an entire second pass over a large structure.

The color it picks is whichever paint sits earliest in your inventory, so keep exactly one can on you and leave the rest in a chest. This catches people out constantly: you pick up a stray can while mining, it lands in a lower slot number, and the next room you build comes out the wrong shade.

On current versions it works from your inventory without being equipped, so carrying it costs you nothing. It also folds into the Architect Gizmo Pack once you have gathered the other building trinkets, which is where it should end up.