Allowing a single application to return themed views without code duplication.
Pre-compiling Razor views to promote code re-use across ASP.NET MVC projects
Leveraging MVC features in a ASP.NET WebForms project
Implementing Dependency Injection using an Inversion of Control container such as Unity in legacy web forms applications.
Leveraging Bundles to optimize legacy web forms applications.
MVC supports Output caching pretty much out of the box, with a little extra configuration it can also be setup to have a dependency on sql server tables.
Creating re-usable MVC views across project libraries.
Using Unity for dependency injection can make your code easier to maintain and test, as a bonus it is fairly straight forward to setup in an Mvc project.
Correctly setting content type when returning JSON results to script from an ASP.NET Web Service.
A Quick Guide to Implementing custom datatypes in Umbraco 7.x