A few examples of ones I have worked at or friends have:

A company that created a novel commercial solar estimation algorithm, and ran a B2B SaaS with it.

A small platform specific agency, 10-20 people specializing in a specific eCommerce platform.

A company that had been producing IoT software and devices for farmers.

A slightly bigger company that produced backbone software for bank management, I think they had closer to 100 employees eventually but the dev team was still relatively small. Bank software takes a lot of extra curricular activity it turns out!