Me, working with an unmarried couple. They've got loan approval, and I start showing them houses in their price range. I show them one they like very much. I offer to buy them lunch. We're having lunch, and they decide to go forward with a full-price offer. I call the listing agent (a reputable agent that I know), and tell him that I will be forwarding an offer later that day. He tells me to expect a quick, affirmative response. So, I then give my buyers my standard speech...don't make any major transactions, don't run up your credit cards, don't change jobs, etc. Don't make your financial picture look even a tiny bit different than when the loan was approved. The man starts acting strangely.
We part so I can get started on writing the offer. He calls me, and speaks in a very low voice. The fucking idiot had gone to a mall jewelry store and purchased an engagement ring for the woman, and had financed it. I called his lender, and the lender is livid. Fucking idiot got approved by the skin of his teeth, and now this purchase will torpedo his chance at closing the loan.