Just waxing nostalgic here, but I fondly remember WordPerfect 5.1 for DOS myself.
I remember buying it for school in 1991 and being totally lost when I fired it up on my CompuAdd 20 Mhz 386sx. So like any good student, I went to work studying the manual and going through all the exercises that were in the workbook that came with the software.
Since I was writing papers in biblical studies, I ordered the free Greek and Hebrew fonts that WordPerfect Corp. provided upon request. It was tedious by today's standards to manually enter one special character at a time, but it allowed me to turn in papers that were a notch above my fellow classmates at the time who were writing original language content in by hand after the paper was printed.
I don't think I ever spent so much time learning the ins and outs of any word processor that I've used since as I did with WP51. In fact, because I put so much time into it, I think that's why of all the software I've gotten rid of over the years, I've still held on to those WP51 disk and that ring binder manual. The only part I don't have is the workbook that I loaned out and never got back.