All the larger baseplates: 6x6, 8x8, 16x16, 16x32,32x32, 64x64
Basically, what i'm thinking is if you could select this brick, place it as a regular ghost brick, and when you plant it, instead of creating a brick, it would delete all the bricks inside the ghost! It would be incredibly useful for the War on Spam, and i'm no coder but it sounds like it would be easy to do.
Please get back to me about this, and for god sakes, SOMEONE MAKE THIS D: