One of the most iconic tiki mugs of all time might just be the Tiki Bob ceramic mug. It was the first mass produced tiki mug sometime in the 1950s for a Tiki Bar in San Francisco by the same name. While the face might seem a little odd, it is supposed to be a smiling tiki carved into the base of a palm tree.
These are not easy to find, but you can find a ton of variations on this theme. On eBay you might be able to find one going for $150 or more as of this writing.
The mug became especially popular when a limited edition run was made for promotional purposes of the Elvis Presley movie Blue Hawaii.