Wow, clearly I'm showing my age here because I can't find a picture either. Back in the 80s a gonzo ball was a bouncy ball cast into a roughly round, irregular polyhedron so that when it hit the ground it bounced at some unpredictable angle.
"Z-ball" seems to be the common name
"gonzo" means crazy or over-the-top
Not familiar with "gonzo ball" but it probably means "large amount of craziness"