For $12, Gama Go will sell you a mould that makes skull-shaped ice cubes. Not technically cubes, though, are they?
P.S. This reminded me that we require pyramid-shaped ice cubes (i.e. pyramids) for our illuminati parties. Unfortunately, all the molds available online seem to be floppy silicone ones with the tops flattened to be stable in the freezer or oven. This is clearly unacceptable -- does anyone make a nice hard plastic one with pointy tops? If not, we may have to kickstart this.