This unique 4 sided die is easier to roll than the standard tetrahedron and it's easier to read the result.
The shape is a gyrobifastigium, an order 2 polyisohedron
. It has 4 square sides and 4 equilateral triangle sides, though only the square sides are stable.
Note that this is a blank, so the faces will need to be numbered. For more information on unique dice shapes, see http://loki3.com/poly/fair-dice.html