Believe it or not, I actually had this question on a job interview application. In addition, it had to be answered in 200 words or less... Truthfully, I could have written 10 pages easily! This is one of those fun, age-old question that will leave people debating for years. Wondering what my response was? Here it is (yes, I had some fun in my response):

This question is intriguing in that it could imply any number of questions such as, "Who would win in a fight?" or even "Who has the best fashion accessories?" Since the question is ambiguous, I will answer both. If I were to bet on whether pirates or ninjas would win a fight, I would put my money on ninjas. Pirates have an ample supply of weapons and use them for brute force, but lack the discipline to use them effectively. Ninjas, on the other hand, have dedicated their lives to training and the skills of martial arts. In addition, ninjas have mastered the art of stealth and are able to sneak up on their opponent. Unfortunately, the main challenge facing ninjas is fighting pirates on the ocean. Instead, ninjas would quietly infiltrate the pirate ranks, taking out the pirates one by one. When it comes to fashion accessories though, pirates are superior. Pirates have body piercings, usually made from the gold plundered on their adventures. But the pirate captain beats them all with an eyepatch, a hook, a pegleg, a pirate cap, and even a talking parrot! Ninjas only get a white or black robe. Thus, pirates have better fashion accessories!

Hey, try to write one yourself - it's fun!