Favorite Interview Questions

I've seen threads asking what kind of questions to expect before going in to an interview, but what about from the other side of the table?

What are your favorite questions to ask someone interviewing for a Linux sysadmin position? Why do you like this question? Also, what kind of industry do you interview for? Questions for a mid-level position at a high frequency trading firm are going to be radically different than those for a position supporting shared hosting customers running cPanel/Plesk/whatever.