I was wondering which kingdom card everyone thought best represented each expansion(I want to play a game with my group that has representation from as many expansions as possible). Here is what I came up with based on the expansions I have(also included an Event for Adventures and a Landmark for Empires):

Base: Smithy - Arguably the most simple card in the game.

Intrigue: Nobles - Includes decision making and a card with multiple types.

Alchemy: Alchemist - Can be chained and heavily revolves around potions.

Prosperity: Bank - Kingdom Treasure and is 7 cost.

Dark Ages: Death Cart - A Looter and involves Trashing.

Adventures: Peasant - A Traveler that includes a Reserve card and incorporates tokens.

Adventures(event): Borrow - An effect that I feel only works because it is an Event.

Empires: Gladiator/Fortune - A split pile that also includes debt.

Empires(Landmark): Aqueduct - Works like the gathering mechanic.

Promo: Black Market - Just the most outrageous effect in the game.