What is the best responsive design you have ever used or tested as a web developer?

Unfortunately, I can’t help you on that as I don’t have such as of skills

well im not a web developer , but i do recomend adobe muse for responsive designs

Your question is not too clear but if you mean the best responsive design *framework* i have ever used, then BootStrap

eny template devloped under bootstrap 

The technical standards of the best responsive web design are HTML5, CSS3 and JavaScript, based on a technique called Media Queries (CSS3). The screen size is used as the unit of measurement for relevant code. It means that CSS can be applied to different devices without great effort. Depending on the resolution ratios, the page layout and size of the elements and fonts, as well as the navigation can be adjusted. You do not have to heavily rely on Javascript or HTML code.

Use Boostrap for best reaponsive experience. Using this you can design best responsive site

First, I am not clear about your question what do you want to say.

Second, Resonsvie design is "Responsive web design is an approach to web design that makes web pages render well on a variety of devices and window or screen sizes. Recent work also considers the viewer proximity as part of the viewing context as an extension for RWD."

And responsive depends on your chess skills, how much deep you know cc's and css3 new skills.