I'm looking for your best "quick answer" technical interview questions. We are a 100% Microsoft shop and do the majority of our development on the ASP.NET web stack in C# and have a custom SOA framework also written in C#. We use a combination of Web Forms, MVC, Web Services, WCF, Entity Framework, SQL Server, TSQL, jQuery, LINQ, and TFS in a SCRUM environment. We are currently on .NET 3.5 with a very near transition to .NET 4.0.
Our interviewing process includes a 55 minute interview with two technical people (usually an architect and a senior developer). The two interviewers have to share the time for questions.
That isn't enough time for very many true programming problems so I'm looking for more good questions that have quick, yet meaningful, answers.
We are mainly interviewing for Senior Dev positions right now but may interview for some Juniors in the future.
EDITED FOR CLARIFICATION: The should not necessarily be specific to the MS stack. I just don't want questions that are specific to OTHER technology stacks like Ruby or Java.