I use Qwen. I have a local instance running on my own AI server I use for proof reading and correcting typos and such and language translation. Its also helpful with Linux and coding questions.
I also use the web version because it's pretty good with parsing documents so you can upload a PDF and have it either find something in it or break it down for you and help you understand it. It's also good with math so I have asked it to help solve certain equations for me or to derive certain equations/formulas I needed.