There are many types and styles of scripts, the one you choose depending on what you are writing a script for.
Just like Treatments, scripts are always written in Courier font size 12.
A screenplay is a common style for video projects that have a narrative and includes dialogue.
The Dark Knight Opening Scene.pdf
Scriptworthy | Tools for a New Generation of Screenwriters
Scriptwriting & Pre-production Tools for Video and Game Production | Celtx