What are your favorite design collaboration tools to use with your team?

I've actually really enjoyed using Keynote. In particular adding graphics, animations, and seeing that experience with actual clicks without going deep on layers etc. has been easy and rewarding

I've used Figma, Miro, and Lucidchart in the past few years for collaborating with my team on product designs. (Usually, we are designing applications and software, not physical products.)

Figma is my favorite because you can make high fidelity prototypes and demos. These are handy for showing to internal stakeholders and even customers to get them on board with the product design, and to solicit feedback before we invest time in building the product. 

I find that Miro is good for getting started with ideas quickly. Is'd helpful for design diagramming and process maps. It makes it easier to plan out a design quickly.

Both Figma and Miro allow you to make comments on items that your teammates can see and address, which make collaboration easy to do within the tool.