I voted "other" because I do not consider the first two options to be Christian. Dispensationalism is dangerous, but (at least from what I have experienced) runs more rampant in the Pelagian and Arminian circles than Christian circles.
As for what doctrine I think is most dangerous, I have a hard time deciding between:
1. Fundamentalism as a "worldview" (vs. Confessionalism - see D.G. Hart's book "Recovering Mother Kirk" and "The Lost Soul of American Protestantism")
2. Federal Vision/Novel views of the Covenant