Tournament, win a prize, drawing it, then immediately upgrade it into a Poor House.
I can't really see wanting to do it that much, but here's a scenario where I believe it's empirically the best play (as it's the only move which gives you a guaranteed victory)
You're 9 points down, there's 1 Colony left, more Provinces than that because your opponent hasn't gained any, no +buy and piles aren't about to run out. Your hand is Tournament/Upgrade/Province/King's Court/Watchtower. The top card of your deck is any cantrip (let's go for Pearl Diver).
You play Tournament, discard the Province, take any prize. You play upgrade, trashing the prize, gaining a poor house, revealing watchtower to top deck it. Then you play your Pearl Diver, drawing the poor house, and KC it for +$12, and buy the Colony for the win.