This is a bit of a staple in the clay artist's toolbox. These little beauties are invaluable to me and I use them all of the time, for cutting, slicing shaping and even lifting clay off my work surface.
 
Please note that these are SHARP, and should only be used by adults. I would also advise marling or tapinf the dull side of the blade in order to ensure that you do not accidentally pick if up the wrong way and cut yourself.