I liked Gallup's Strength test. It seemed somewhat less susceptible than the average to confirming prior assumptions, and at least for me it gave some interesting thought-provoking results. I'm not sure it gave me any genuinely new insights, but it certainly sharpened previously vaguely-formed feelings into something I could more readily understand.
As an aside, the different strengths all represent different ways of looking at and appreciating the world. My reaction upon reading half of the strengths were "wow, there are people who think like that?", while to the other half my reaction was, "wow, there are people who don't think like that?". For me that was the greatest antidote to the Typical Mind Fallacy that I've ever come across.
Actually the most useful thing I've gotten out of the test was as a tool for gaining insight into others. I asked several people whom I work with to take the test, and then we went through the results together to see how exactly each strength applied to them in particular. The results were definitely eye-opening.
For example, one of my employees had the Arranger strength as a leading strength. Amongst other things, that implied that she enjoyed juggling the demands of many different projects all going on at once. I asked her if this was accurate and she replied that not only was it true, but it also caused her to be bored out of her mind in her old job where there were only ever one or two things going on. I can't even begin to identify with this (I'm the opposite - I like one or two projects and more is way too much), and I would never ever have thought to ask if she wanted yet more things on her plate. Yet that's exactly what she wanted and she was very excited when I handed over several additional projects to her. And here I thought (Typical Mind Fallacy!) that I was overloading her with what I had already given her.
Have you ever taken a personality quiz/test that helped you have valuable insights? If so, what were the tests and how were they useful?
The only useful ones I've found all yielded the same type of insight. They showed me where I stand relative to others, which is can be genuinely useful since representative samples of large populations can be hard to come by. This includes IQ tests and tests for mental disorders (in my experience, people are usually aware that they are, for example, smarter than the average (although the Dunning-Kruger effect might complicate this) or have some intrusive thoughts and compulsive rituals, but might be surprised to find that they are three standard deviations above the norm or that their symptoms are sufficiently severe to be considered OCD).
No remotely reliable (as in, not astrology) test I have ever seen has revealed genuinely surprising information for a moderately self-aware person, outside of ranking. Furthermore, they rarely gather personality data in a remotely subtle or non-transparent way ("do you like spending lots of time with large groups of people?" "yes..." "surprise, you're an extrovert!"), and thus seem super susceptible to test-takers' attempts to confirm a desired identity.
An example of a more interesting/subtle way to potentially conduct a personality test would be to use question like OKTrends' "do you like beer?" which clusters strongly with "do you have sex on the first date," and, potentially, sexual openness. Such results might be harder for manipulate (consciously or unconsciously) and could assist with deeper self-awareness.
Edited because the first link was broken.