REI is an interesting example. It's a co-op in name, but the employees don't have much representation at the top. (See:
http://www.thestranger.com/slog/2016/07/11/24328725/rei-work...).
There are lots of great companies that are employee-owned (the Winco chain of grocery stores comes to mind), but I'm not aware of any in the tech startup world.
I'd love to know about market research companies with an employee-owned model! If you know of any specifically, let me know. Google doesn't seem to be of much help.