YouEatPig
Terrarian
I think this would be extremely useful for building in Terraria. A keybinding would select the block/wall/furniture on the cursor, and if the player has it in their inventory, allow it to be placeable. Pressing the key again would put it back in the slot in the inventory. The game Factorio has this feature, and I would suggest looking at that if you want to see the idea in practice.