Flash (Animate) is still my favourite mockup and design tool. It used to be so much more powerful in that you could export to a lot of different formats. And when your output is just some standard format, it didn't matter what the creation tool was. I could manoeuvre faster in that application than any other tool. And the bonus was that for anything you designed, it was almost trivial to animate it. I now find myself doing svg animation using it + plugins.

Adobe has constantly killed features in it but I still love it.

it was all Macromedia at one time (before Adobe felt the competition, bought the whole company and rebranded the suite that included Flash). Macromedia Director had an even more powerful set of tools, until Macromedia Flash evolved the ActionScript language and with web dissemination really took over.