A great "representative" question should meet all of the following requirements:
It is of general interest to a recognizable subset of the culinary community. Mass appeal appeal is not required, but "what went wrong with my recipe?" questions generally don't fit the bill - although we might want to pick one or two, just to show that they get answered nevertheless.
It has a highly-voted or accepted answer that is not just good, but illuminating. We don't want the kind of Q&A where people read it and go, "Yeah, that makes sense." We want people to read it and go "Wow, I never would have figured that out!"
It is not already trivial to answer with Google or another well-known site (Wikipedia, stilltasty, chowhound, etc.) We want questions that show not only that we're good but also unique.
Please let's not make this into a poll. Instead, add your own examples to this answer, along with a short (one reasonably-sized paragraph) explanation of why you think it fits the bill. The starter list is taken from yossarian's link in the question - I picked my top 3.
Why can applesauce be used in place of oil?
There is an astounding amount of awful misinformation to be found on the internet about this substitution. All of the top Google results are total crap; none explain anything in detail and most give advice that's naïve or just plain wrong. I (Aaronut) have beefed up my answer with a bunch of sources and tried to set the record straight; fact-checking is, of course, welcome.
Pasta: Simmering Water or Rolling Boil?
Almost everybody makes pasta from time to time, and although you can find reasonably-correct information on Google, most of the hits don't tell you the whole story. I think our question does an excellent job of highlighting the competing viewpoints (as separate answers) and their relative merits without overwhelming the reader.
Why do some recipes recommend Kosher salt?
Nowhere else have I found this kind of information, and yet it's very important to know if you have a recipe calling for kosher salt (and most people who cook regularly will have seen at least one).
How Could I Make Stuffed French Fries?
I love a bunch of things about this question. A google search is useless as it's a relatively original idea and the words are so common. A search for "Stuffed French Fries" either in quotes or out turns up nothing of value on page 1, except this question which is ranked 1st. Most of all, someone in the community who's in the restaurant industry thought it was interesting, didn't know the answer, and spent a day playing around with techniques, eventually landing on one.
How can I make a chocolate cup that looks like the seaweed on a sushi roll?
This is another "Seasoned Advice Original" in that it's high on the "cool factor" and you won't get many other Google hits on it. Great for showing how we're about much more than bland and generic home cooking.