I'm looking for a synonym of useful, with a maximum grateful attitude. It is not a person to be thanked, but an idea. It mostly a breakthrough idea, but breakthrough is not what I'm looking for. I have found some synonyms of useful on Google, but I'm confused how to choose one:
functional, practical, handy, convenient, utilitarian, serviceable, of use, of service, beneficial, advantageous, helpful, worthwhile, profitable, rewarding, productive, constructive, valuable, fruitful
To get you understand sense of the word, here is an example of it. In theoretical physics, physicists have to deal with tons of mathematics, and physical meanings usually be buried in the lines of
code math. For example, the collision of two particles has this mathematical expression (I'm trying to trim a lot of jargons here):
Compare to a real world collision:
What a _______ idea!
Image and expression taken from the wiki page of Feynman diagram.