Oracle is very popular for mission-critical databases in banks. I've seen Sybase used in banks too but it's definitely less popular now than it used to be.
Oil/Gas exploration. In my former job, pretty much every major piece of software that we sold to customers had at least an embedded Oracle DB as part of the install.
In industry, all I've ever seen is Sybase, SQL Server, and MySQL (ok, technically Oracle). (My background is finance and technology.)