Object Initalizers aren't talked about very much as one of the new features in C# 3.0, but I find them pretty useful from time to time (esepcially when dealing with the SharePoint API). They are great, when there isn't a constructor that has all of the arguments that you need to initialize the class with in it. Here is an example of how I used it lately with the KeywordQuery class.
KeywordQuery myQuery = new KeywordQuery(siteCollection)
{
QueryText = string.Format("Color:\"{0}\"", myColor),
ResultTypes = ResultType.RelevantResults
};
In this case I wanted to initialize the QueryText and ResultType properties. This makes the syntax much cleaner. Obviously this feature isn't life changing, but I find it a nice convenience.