I am trying to figure out how to have trials presented randomly but not having to define every single trial before hand. Basically I have 20 choices that participants must make between two options. I want these choices presented in random order and only once.

If I were programming this in anything else (presentation, realbasic, etc...)  I would simply define an array like

Array X = (10, 20, 30, 40, 50, 60, 70, 80, 90, 100)

I would then shuffle array X so it is in random order and then work through replacing the parts needed with something like replace item = ArrayX[ n ] where n is a value that increases with each trial.

I dont see such a framework being possible in Inquisit in a straightforward way. Any thoughts on how to implement this?

This can be easily achieved with a single <trial> element, sampling determined by the stimulus elements it presents. Not sure why one would need an array construct here.

However, <list> or <counter> elements offer much the same functionality as classic arrays, in case you really need that.

Perhaps its just my way of thinking after programming for so long using other formats. But my current employers want to use Inquisit as its simpler for a lot of the people in the labs to put together their experiments but it seems to lack a lot of programming freedom other systems have. 

I dont understand how I could do this with a single trial. I looked at list and it looks like it might work so I will give it a shot. 

Studying a few of the more complex scripts in the Task Library might prove worthwhile, such as Information Sampling Task, Tower of London, Columbia Card Task. You will find that traditional programming techniques apply to Inquisit syntax as well.