“Some that came to mind were WordPerfect 5.1, Netscape Navigator, Dreamweaver, Eudora, and an old version of Paint Shop Pro that I used for many years.” …… Hey, you’ve been living my life. LOL

I would have to say Firefox — it dragged us out of the chains of IE/AOL into a better place, even if I have now defected to Chrome, but FF was the leader.