After slaying unique pixels or "bosses" in various MMORPGs, a specific item from a random total pool of items may appear. When desiring certain items and seeing possible alternatives, one often wonders which might be better suited for them. It is then someone may say "WDF" as a response, suggesting that the item that appears first should be used, instead of their alternatives.
Person 1: "Would you take item1 or item2 as your item of choice?"
Person 2: "WDF"