If there is one game mechanic I always like exploring, it's Reiner Knizia's "lowest set" victory condition. The gist is that you're building up several resources throughout the game. However, your final score is based on the lowest of those resources. To put it another way, you score one point for every complete set of resources. It's a clever mechanic that spreads your strategy, often because obtaining each resource requires very different tactics.
I recently played Cosmic Encounter for the first time, which has also infected my brain a bit. In the basic game, each player begins with a certain number of ships on each planet of their solar system. You win by getting one or more of your ships on five different planets outside your system. You do this with direct attacks, bribes, exceptional faction powers and special action cards. I really loved how such a simple victory condition diverges into numerous strategies.
So, naturally, these two influences mixed up in my head to this odd little idea. I have no idea if it works properly, but I'll just toss it out for you to chew on.
Three or more players are traders sent from different countries to exchange goods. Each player begins with 10 resources, randomly distributed among four categories: A, B, C, D. Your resources are kept secret.
Your goal is to have the highest score by the end of the game. The game ends when one player has a certain amount of a single resource, usually something high like 8 or 10 depending on the number of players. Your points are equal to your lowest resource. Thus, if your score was 5A, 2B, 6C, and 3D, your final score would be 2.
Gameplay involves trading resources in secret with the other players. You may each propose a trade, but do not reveal your cards to each other until after making an agreement. You may make a "dirty" deal, by lying about what it is you're actually giving the other player. Throughout each interaction, the central dilemma persists: As you pursue the endgame, you may be helping your opponent achieve a better score.
For an extra element of weirdness, you could even use the Yspahan-inspired card deck from this post. Thus, rarity becomes an additional mechanic, perhaps acting as a score modifier. The resources are the suits, but bonus points come from matching colors.