Microsoft OneNote
I've always been interested in note-taking and productivity software. I've used Evernote for a few years now and always thought this was the best product available. Whilst Evernote has had its issues, it does seem to be getting back to it's prime, even if it is much more expensive.
I recently watched this video from Tiago Forte's YouTube channel. It features Matthew Gilbertson as a guest, explaining how useful OneNote can be.
I've started testing it out for myself and will report back after a few weeks/months.