One trend in craft cocktails is to have large ice cubes, some with interesting shapes.
For instance, you've probably seen large round ice cubes in a lowball glass, and some would tell you that this creates the perfect drinking experience. Due to the density of the ice ball, it melts more slowly and thus doesn't water down any expensive alcohol in the glass.
But also, it just looks cool, and it was only a matter of time until these master bartenders started branching out into even more shapes.
He takes a razor sharp knife to a block of ice to begin carving it into the desired shape.