Rob Neu wrote a ridiculously long, but very high quality, listicle of the best WordPress plugins “since the dawn of time.” I don’t agree with every single one of his picks, but he has tested them all and they definitely each have solid justification.
I learned about a number of them for the first time. I don’t often link lists, but this is a very good list and its worth reading his explanation, versus just skimming through the options.