Combo: Bishop and Fortress
From DominionStrategy Wiki
Bishop/Fortress is a special kind of Golden Deck that can exist in the absence of Chapel, and which can cause the game to last indefinitely long. The end state of the deck is Bishop x4, Fortress x4. Each turn, the Golden Deck player has at least one Fortress in hand, so he plays Fortress x3, drawing everything from his draw pile and accumulating 4 actions, then plays Bishop x4 on the remaining Fortress, generating and a whopping 12 . As long as the state of the deck does not change, it can go on like this until the end of the game. This can make for indefinitely long games, as the Bishop/Fortress player has no incentive to buy any cards with his .