Firefox

I love kde for the functionality and the development skills. But I like the GTK adwaita style a lot more and gnomes design improves every couple of months although all the apps are in a different state right now which isn't the case for kde. Kde apps all look consistent but that's just because nothing has changed in the past years I guess. Moreover writing apps with GTK seems to have a lower barrier to entry with python et al compated to C/C++