Cold-called by an Apple recruiter regarding a Face Recognition engineering position. Received a phone interview with an Apple director; then an all-day interview which included a VP, director, architects and managers - followed by another all-day interview including team members. Then I went through a month of background checks and negotiations. I found it helpful to bang out a face detection iPhone app the weekend before my first interview - it gave me something to demo and talk about the pros/cons involved in the effort. Now that it's out, I would strongly recommend doing a demo on an iPad. Be prepared to do whiteboard design, developing algorithms on the fly, coding problems, and demonstrate your problem-solving process.

Design a scene graph object class, without knowing a target use case.