What is a wiki?

Assuming you've been exposed to these, it's fine, but personally, they drive me up the wall. ;-)

What is a Design Pattern?

It's been so long since I left school, that I don't remember formal definitions. But do you think that I'm a bad fit for your company just because I've been away from school for nearly a decade?

What is a Code Smell?

If it weren't for PM, I wouldn't have heard of this term. It's just a bit on the obscure side, IMO

What are agile methodologies? (for example, Extreme Programming)

Ask only if you religiously follow them because you want to know that the interviewee will be able to follow them. I'd flunk out of your interview here.

What is Test Driven Development (TDD)?

Isn't this exactly what the name implies? ;-)

What is xUnit? (e.g. SUnit, JUnit, cppunit, NUnit, ...)

No idea. ;-)

Have you heard of Subversion?

Isn't that the VCS that Linux used to use? Do you actually use Subversion? Or do you really only care that the person has been exposed to version control systems, and are willing to retrain for your specific VCS?

Why do you want to work at our company?

Because I'm unemployed and need some money?

What are you good at? Bad at? Enjoy? Dislike?

I'm good at coding, bad at stopping at 5 when I've got a deadline looming, and I extremely dislike personal time. If this isn't a question screaming for a cover-up, I don't know what is.

What are your favourite books/magazines/web sites?

Your company's website is my favourite. Seriously - do you want a perl geek who lives for perl, or do you want a well-balanced individual who has multiple facets to their lives and thus can think in many directions?

What are your favourite tools? For example, if you start a new job, what tools *must* you install immediately?

Perl?

Tell me about the worst bug from hell (e.g. intermittent crashing program) you faced and how you solved it.

Now we're getting somewhere. This is a question that is much harder to lie on, and will tell you a lot about the person you're interviewing. You'll see what they've done, and how they handled it. Which is important - because theoretical questions are fine, but they don't face the same time constraints as real problems. Asking, "How do you handle a bug" allows someone to wax eloquent on theoretical bugs. Asking, "How have you handled the worst bug you've faced" goes back in time to a point where they had real pressures - other classes if in school, or project deadlines if in a previous job, personal problems at home, whatever. You'll see what shortcuts they took, if any. It's a very powerful question.

Describe in detail a recent project you developed that you are proud of.

You may want to ask this before the previous question, and then focus your debugging question on this project. Also, ask about the role the person had in that project, why they had that role, etc.

Just a few points. Remebering that most people lie in an interview, you want to not ask open-ended questions. You want to ask very specific questions that get at the information you need. Most people don't intend to lie. They just do.

Interviewer: Does your mind ever wander during meetings?
Interviewee (to self): I can't remember any such time, so...
Interviewee: No

It's just a mix between trying to put your best foot forward, and not necessarily remembering everything in the heat of a short (30-90 minute) interview that would be easy to recall when the deadline is further away (say, end-of-day).