Standard Chartered is one.
https://twitter.com/donsbot -- author of Real World Haskell
See https://wiki.haskell.org/Haskell_in_industry for more.
Several other financial names including Bank of America Merril Lynch, Barclays Capital, Capital IQ, Credit Suisse, Tsuru Capital are listed.
They even have their internal Haskell compiler which IIUC gets fed a dialect in order to have strict evaluation and a couple other non-standard properties. One nice thing the ecosystem got from their internal team is the official Shake implementation, which supersedes the various 3rd-party implementations and actually works really well. It even can interpret Ninja files, so it can be used in place of ninja when building things like Cmake-based projects or, say, Chromium. Not that there much of a reason to use Shake when you use Ninja, but you can and some of the reporting features might be exclusive to Shake. Usually you write a Shakefile.hs (instead of Makefile) and run it with shake.
Places to spot then:
Mind sharing names?