"It proves my gizmo really works."
Okay, prototypes don't really have to be pretty. They aren't unbreakable or ergonomic. And they don't have to cost a lot.
But! Remeber Mom's rule of "first impressions". Your prototype should grab instant interest. It should reflect purpose, potential and opportunity.
Check these floatable boats, built from cardboard and dreams. Does your prototype excite such attention...at first glance?