Hi trevorc1653,
Thanks for your passion about our products! It's really great to see.
While I can't reply in an official capacity about what our 'flagship' product is, I can certainly say that FortiGate is the product for which we have the most documentation and support, and it is our most widely-used product - front and center on our product page.
The specific FortiGate product page explains more about its use:
If you're looking to get a deeper understanding of Fortinet products as your other post indicates, FortiGate is the perfect place to start due to its broad use and how closely tied it is with many of our other products.
I hope that helps,
