1. "Gloomy Sunday," preferably an early Billie Holiday version, but I'm not going to get picky with you
2. that guy who yells, "Sunday! Sunday! SUNDAY!"
3. yelling it yourself, just because you can
5. this statement on Wikipedia about the mysterious/contested origin of the term "sundae": "[some claim] the name "sundae" was adopted as a result of Illinois state's early promotion of ice cream consumption on Sundays, because ice cream with a topping that obscured the main product was deemed to be delicious."
6. wanting to know who, exactly, felt the need to do the deeming. Ah, passive voice. You are so mysterious!