[unhammer]

One that I use all the time is shellcheck, and git-annex. Others in the mainly-used-by-programmers-category include xmonad and hledger. https://github.com/owickstrom has some GUI Haskell apps.

Facebook's Sigma and https://github.com/wireapp/wire-server may be the ones with the most non-programmer users?

http://postgrest.org/ and https://hasura.io/ seem interesting.

https://www.quora.com/What-is-the-largest-commercial-program... says the largest Haskell code-base is probably Standard Chartered trading system.

more at https://github.com/topics/haskell and https://serokell.io/blog/top-software-written-in-haskell