Jetbrains, Rational, Perforce, MySQL, GitHub, Trello, StackOverflow, Joyent, Powershell, etc as well.
The tricky part is that to monetize, you either need to master enterprise sales (which means that the product will take on some PHB-pleasing features that developers despise so they can get through procurement departments), or you need to be acquired by a big company looking to round out their developer tools offerings.
