<summary>
GhostDoc is a free add-in for Visual Studio that automatically generates XML
documentation comments for C#. Either by using existing documentation inherited
from base classes or implemented interfaces, or by deducing comments from
name and type of e.g. methods, properties or parameters.
</summary>

The XML documentation comments of C# reward you in multiple ways: Visual Studio shows their content on various occasions (e.g. in tooltips in the text editor, or in the object browser), and some tools (e.g. Microsoft's documentation named Sandcastle) can generate nice looking help files for you. So overall, writing XML documentation comments sounds like a pretty good idea - unfortunately it often consists of a lot of stupid work that simply has to be done.

Some things are especially tiresome to document, e.g. implementations of interfaces or overrides of base class members. Often enough the documentation already exists but has to be copied manually over and over again. And then there are fairly obvious language elements like constructors (with a typical summary of "Initializes a new instance of the <see cref="Foobar" /> class."), or properties (remember how often you write "Gets or sets ...", or worse "Gets or sets a value indicating whether..."?).

If you feel that you spend too much time on writing "bread-and-butter" texts, and too little time on finally adding that bit of really valuable extra info, GhostDoc is for you.