Many of productivity tools I use are free (and not always related to dev, but as a side effect, increase my development productivity as well):

* a big monitor (switching from 13" to 27" definitely had an impact)

* https://www.raycast.com/ has the biggest impact to my productivity. So much good stuff there! Just one example is resizing windows with keyboard. Good old https://www.alfredapp.com/ is another option;

* https://devdocs.io/ to look up docs;

* https://www.tldraw.com/ for temporary sketches, wireframes, etc.

* while I'm here: in my experience, one-time purchase from https://serif.com/ is a great alternative to Creative Cloud.