Most are made up and silly.
The only one I've liked was in college I did a "communication style" one. Where it showed a bunch of different like emails, posts, and conversations and asked which you preferred to receive and which you were likely to write.
10 years later I still think about it, cause the goal of the work was to talk about how if you're a certain communication style what to keep in mind with communicating with others. Like tips to not get frustrated with yellows who don't care about facts when sending emails and how to write emails that don't bore and frustrate people if you're blue. (I'm blue green. I can sometimes write long emails)
I thought about it the other day cause a guy was complaining about all these emails that didn't seem to say anything, they were just about feeling good, and he just wanted them to spit it out. Which corresponded to firey red getting mad at green.
So with that context, do you have any that actually had an impact on you?
I have done many.
"Helpful" needs to be defined. In my younger life it helped me to find out about my personality. Later it also helped to understand other people.
Sometimes these tests gave contradicting results, so I learned that these results can never be taken 100% literally. You have to decide what to take from it and what to leave.
MBTI was the first one that fully admitted this, and that book even explained how these things change when you get older. So I consider this the most helpful one.
The strongest one IMHO was the Enneagram. But also most hard to understand.
The most scary one (and in retrospect, the most funny one) was at Scientology. It helped me to understand what a bunch that is and how they can catch people.