Okay another one I thought of, with a simple puzzle.
All cards are in the supply. Pick 5 cards out of them and put them in your hand (nothing else is in your deck). Now end the game with a three (or more)-pile.
I have an alternate ending that is more complicated. I'll put that in another post.
King's Court, King's Court, Bridge, Ironworks, Ironworks.
Play KC-KC-Bridge-IR. Gain Nobles, Nobles, KC. (the Nobles come into your hand).
Final KC is the other IR. Gain KC, IR, IR.
Play Nobles for +3 cards and then the other Nobles for +3 cards.
Hand is now KC, KC, IR, IR.
Play KC-KC-IR-IR gaining Nobles, Nobles, KC, KC, IR, IR.
Final KC is Nobles. Draw all gained cards.
Hand is now KC, KC, IR, IR, Nobles.
Play KC-KC-IR-IR-Nobles, gaining KC, KC, Embargo, Bridge, Squire, and draw them into your hand.
Finally play KC-KC-Embargo-Bridge-Squire.
Embargo Duchys. When playing Squire, always select +2 buys.
You now enter the buy phase with cards costing 6 less (Duchys are free) and 13 buys.
Buy eight Duchys, taking eight Duchesses and also emptying the Curse pile.
Then buy the last two Duchesses. 3-pile on Duchy, Duchess, and Curse.