Communifire is a fantastic intranet app. It is extremely flexible and robust. One of the more interesting aspects I appreciate is there are many different types of templates/content but, from the users' perspectives, the UI/UX is extremely similar. I think this uniform template format benefits users because they can quickly master all template types in a short period of time.
I also like how each space can be independently configured with a myriad of settings and options, allowing you to control what each user/group will see. I really like the user permission system too, allowing role-based rules for each content type within each space. Review collected by and hosted on G2.com.