A d4 in the shape of a "square edged cigar" as mentioned here:
Alea Kybos Dice Shapes or a Steinmetz Solid (the intersection of two cylinders).
This version is numbered 1-4 rather than with football termanology like the one shown in the link. It is also rather short, like a cigar butt that has been smoked down.
PeterFriz offers a pipped version of a similar shape here:
Peter Friz D4
ppoz offers un unlabelled version of a similar shape here:
Steinmetz Solid D4 Dice
I offer an elongated version of this shape (
labelled or also
unlabelled) which is closer to a "square edged cigar" shape and would be considered a
long die.