In my family there's something we simply call "The Alphabet Game". It's pretty simple: pick a category, the more defined the better, and then take turns going through the alphabet and naming something in that category starting with that letter. For instance, if the category were "Cities in Europe", the first person might say "Aberdeen" and the second "Berlin" and the third "Copenhagen" and so on. It's a handy little game that requires no cards or dice or paraphernalia of any kind. We've relied on it many times in the car on long trips, and I've summoned it plenty in my own head while at the dentist or sitting in traffic.
Scattergories is sort of the inverse of that exercise. Instead of taking one category through all the letters, you take one letter and apply it to twelve categories. Instead of being cooperative and open-ended, this game is competitive and ruled by a remorseless minute glass. Like all great games, it's quite basic. Write your answers down on the sheet, and then compare them with your foes. If you have an answer no one else has, you get a point. If you have the same answer, neither of you scores. If you leave it blank, you get nothing. If your answer is determined by the players to be inapplicable in some way, you get nothing. After playing twelve sheets of categories (or however many your stamina allows), the player with the most points wins.
I bring up two pitfalls that have personally plagued me while playing this game. First, when playing with good friends, you run the risk of being too much on the same wavelength. This past summer, my buddy Bill and I were all too often stymied by providing identical answers a disturbing amount of the time. I knew we were pals for a reason, but come on, man. There's also a proviso in the rules that if you provide alliterative answers, you can score extra points. My wife is the unquestioned mistress of this particular maneuver. So the die says "H" and the category is "Games"? I might answer "Hangman", but here she comes with "Hungry, Hungry Hippos". She's like a three-point sharpshooter in hoops. You think you've got her contained and here come the trifectas.
Probably the most beautiful moments in Scattergories come from the instances of shared delight and frustration. When someone lands a clever response to a thorny category, for instance, and the table nods their grudging appreciation. Or when the players stare at each other in shared blank failure, muttering, "I got nothing". It can be a fun and humbling game. Which makes it great.