At the end of the movie, we see a sales conference in New Zealand where Belfort goes around the room asking newbie/aspiring sales professionals the same question. "Sell me this pen."
Of course, no one in the crowd gets it right. They ramble on nervously about how great the pen is, how you can write upside down, etc. So what exactly is the correct way to answer this open-ended question if it comes up in your next job interview?
First, this question IS too open-ended. You can't sell a pen (or anything) unless you ask questions. If an interviewer asks you to sell him this pen, the correct answer would be something like:
"First, I have no idea the context in which you are asking me this. How long have you been in the market for a pen? What type of pen do you typically use? Etc."
You need to be asking questions to qualify. Otherwise you may be selling something to someone who doesn't need it. This IS THE CORRECT RESPONSE. No matter what. Any interviewer with half a brain will understand this. If they don't, you're probably interviewing at the wrong company. Without understanding the context, it's impossible to sell anything.
Yes, it's an open-ended question. So ask questions of your own to figure out if the hypothetical buyer (the interviewer) even needs the pen. And what he looks for in a pen. And how often he uses a pen. It's that simple. Sales is about asking questions.