Dominion Regional Qualifier
I noticed they both bought Outposts, widely considered one of the worst cards in the game.
I used Ambassador to put my least useful cards into my opponents' decks, and Salvager to recycle the rest for money. This left me with a tiny powerhouse deck of cards into which I put two Treasure Maps, and used Haven to store them so they came up together. The Treasure Maps put four Golds on top of my discard pile. My opponents complimented me on these fancy stunts and said they were in awe. We all agreed I had the game in the bag.
But when the score was counted, I lost by four points. It took too long to set up all those flashy stunts, and I wasn't able to catch up on their early lead.
But no matter! I won the new base card reprints with gorgeous illustrations! I got into the elimination round! It's been an incredible day.