I don't mean the clothing retailer, or even merely the
political science term in its broadest since, but instead something matching O. Henry's original use to describe his fictional Central America country of Anchuria in
Cabbages and Kings (1904). The banana republic then is a sort of sultry colonial companion to the Old World charm of the Ruritania: A fictional, politically unstable Latin American or Caribbean country under the thumb of foreign interests. In gaming terms, it might be the more cynical (and perhaps more interesting) result of the standard D&D endgame.
The real world prototype of the banana republic was Honduras in the late 19th to early 20th Century; a nation that fell more and more under the thrall of U.S. fruit companies. The mercenary army of the Cuyamel Fruit even toppled the elected government and installed General Lee Christmas as commander in chief of the Honduran Army and U.S. Consul. Guatemala in the 1950s shared a similar fate when the elected government was successfully painted as pro-Communist to the U.S. government because they were anti-the United Fruit Company. These examples have the banana republic essentials: greedy foreigners, downtrodden peasantry, passionate revolutionaries, corrupt oligarchs, violent mercenaries, and torrid jungle.
In real-life, adventurers (we could even call them murderhoboes) like
William Walker set up regimes pretty much fitting the banana republic mold in the mid-nineteenth century. Unlike the
Ruritanian Rogue, your foreign rogue in a banana republic might be a central player in the countries woes instead of just having to deal with them.
Here's a
list of fictional Latin American countries. There were a lot of likely banana republics in 80s TV and film, though they weren't always potrayed specifically in those terms. Good examples include Costaguana from Joseph Conrad's
Nostromo and Queimada from the film
Burn! (1969). Though the
Zapata Western (either in its Italian or American form) is always set in Mexico, its themes, roquish characters, and ample
chili con carnage are good inspirations for a banana republic based game.