It'll melt twice as fast as a normal ice cube though, and you need a freezer that can do at least -20C (mine does) to get it to freeze in the first place.
Antifreeze ice cubes -- too funny! Has anyone ever thought about buying 7 different colours of square tiles and tiling a floor or wall with them in a Tetris pattern? It seems like it would be a neat do-it-yourself project.