Spy vs. Spy: The Island Caper (lost build cancelled US localization of NES game based on comic strip; 1989)
Spy vs. Spy: The Island Caper (南国指令!!スパイvsスパイ, lit. "Tropical Directive!! Spy vs. Spy") is a multiplayer platform game released by Kemco for Famicom in 1987, a port of the Commodore 64 version. The Famicom port was also planned to be localized and released on the NES in the United States in 1989, but was cancelled for some reason.
On Mad Island, a mysterious island in the South Pacific, you must find all the missile fragments hidden on the island before your enemies do. Beware that the island is booby-trapped with various booby traps to stop you.
On December 1, 2015, a prototype ROM was listed on eBay with a opening bit of $999. The prototype was subsequently purchased, but it is not currently possible to confirm how much it sold for. No purchased prototypes have surfaced online as of 2023, and this is the only prototype that has been identified so far.
From WorthPoint. Screenshot of the title screen, which the seller seems to have personally dumped and emulator-retrieved.