I failed my first time because I took too long to get into the parallel parking space. I did just fine on everything else though, it's just an instant fail if you take too long.
I had a friend who once failed the test because of his own insistent stupidity. He stopped at a stop sign, and the instructor told him to go ahead. His response?
"Are you sure I'm not on the white line?"
"You're fine, just go."
"You're sure?"
because of his prodding, and to make him happy, the instructor got out with a ruler to check for him. He was an inch on the white stopping line, and was failed, as per the rules (running a stop sign).
Just a bit of advice to those of you taking your driving tests on closed courses, watch out for traps! At the DMV where I took my test, they had a closed course that was kind of like a small loop outfitted with obstacles and what not. If you come to a turn, accentuate your looks in both directions, even if there is no road there. The rule of thumb is this: Chin to your left shoulder, chin to your right shoulder, chin to your left shoulder, chin to your right shoulder. Just glancing out of the corner of your eye doesn't always work, and your instructor may confuse that for not looking at all. Also, they often hide a stop sign right at the end of the course. They'll tell you "Okay, we're done. Just go ahead and pull out of the course and park in an empty space." There will often be a stop sign right at the exit to the course. If you don't see it and stop, you're failed for running a stop sign.