I am pretty confident that I'm one of the IST types. I tend to think ISTP is more like me but I have a lot of traits that are associated with ISTJs. 2 things that make it hard to settle on is that all of my functions have a tendency to go back and forth between E/I, and that I kind of purposely encourage that because I like to be balanced. It's not really a big deal to me either way, but it'd be nice to be more sure of it.
Thinking is the function I feel like I'm best at. I like to have as thorough and complete an understanding of things as possible, I don't like to rush into judgement. That type of thing gets people into trouble. On the other hand I think that my detailed knowledge/opinion on a given subject is only worth something if it can be applied to get concrete results. Also lots of minor everyday things are simple enough that it's better to just take care of them and not think about it too much.
Sensing is the function I feel is most important for people to become good at in general. I think things need to be evaluated based on their own qualities/merits, and that it's better to pay attention to what is going on around me then to be reflecting on it, I can do that later. I do have a small set of things that I have a very strong idea of what is the "right way". I believe that commitments need to be honored and that it is better to be conservative and make sure any changes I am making in a given situation are for the best and not a knee-jerk reaction. At the same time I'm quite good at reacting to immediate danger and adapting to things I didn't see coming.
I think my Intuition is the only function that stays firmly in one orientation, that being Introverted. I am better than most people I know at thinking of different ways something can go and adjusting accordingly. I do very well with both academic tests and real world applications of logic, partially because I am very good at figuring out things I don't necessarily know on the spot based on the clues that present themselves. Sometimes I apply this to other people, usually when a friend asks me for advice and there isn't an obvious solution. I don't use it too much on my own relationships though. I have a very unified internal vision, and I think most things are connected on some level. I definitely go from the many to the one and not the other way around. Like with Thinking, I am only interested in using Intuition to gain tangible results and I have no interest in theory just for it's own sake.
I think Feeling is my most simplistic function and is definitely the one I'm least comfortable. I think it mainly manifests in a feeling of obligation to others and a desire to serve. I like to help others whenever possible but I also firmly believe that it does no good if they aren't willing to help themselves. I also think that it is important to not deviate from my values without very careful consideration, I'm not really all that impressionable of a person.