I've been using Firefox since it was called Netscape, and before that I was using Mosaic. Nowadays, I'm also using Safari (and Vivaldi) but I still can't imagine not using FF as my default browser. More exactly, FF with the uBO extension, which is another nice gift to all of us — a bit like FF pop-up blocker was back then.
I would have loved if they had released an anniversary icon for FF. Too bad they did not, but that's probably just me getting old, all nostalgic and sentimental :p