In my opinion, Rita Mulcahy's PM Fastrack is the best PMP exam simulator. It is ahead of the rest in several terms of quality of questions, number of questions, simulator features and software quality. It comes with 1500 questions and the question format, quality and standard is very close to the real PMP exam.
I used it personally for my preparation and would highly recommend it. The only con is probably the cost. If you cannot afford it, I would suggest you to look at BrainBOK PMP Exam Simulator. It offers 1000 sample questions, 2000 flashcards, world's best ITTO tool, quizzes, formula guide, course completion certificate and much more for just $99.99. This is by far the best tool to prepare for the PMP exam.
Tip: Even if you use a particular exam simulator, attempt at least couple other free mock exams as well. Remember the investment principle - do not put all your eggs into the same basket!
Last Update: Feb 5, 2016