Virtually everyone uses bits of OpenBSD. Android uses a lot of its C standard library, LLVM uses its regular expression library, and Windows 10 uses OpenSSH with LibreSSL.

Armorlogic, Calyptix Security, GeNUA, RTMX, and .vantronix make network appliances based on the complete OS.

I used OpenBSD in production at my previous job (an ISP), in a few different roles. Lots of ISPs use OpenBSD for various purposes.

HSMs from nCipher used to run on top of (a slightly modified, IIRC) OpenBSD. Just as JunOS (the OS on (some) Juniper network devices) runs on FreeBSD, I'm sure there are many other commercial products built on OpenBSD as well -- we just don't hear about them very much.

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Related (from the same author as this submission): "Why OpenBSD?" [0].

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[0]: https://www.cambus.net/why-openbsd/

An acquaintance is currently building the tech part of his and some friends' start-up, entirely on OpenBSD - PHP-based web front end, back end, Postgres-based database, mail server etc.

Not sure if this counts, but I use it in production in yakdocs.com and yak-mu.com. I love how easy it is to maintain and I love the pf firewall. Hetzner has images for OpenBSD on their cloud service and you can use a custom image on the dedicated servers.

Netflix uses freeBSD does that count? https://www.youtube.com/watch?v=KP_bKvXkoC4