It's a difficult subject to study because people are not likely to reveal their more taboo fantasies. Furthermore, in my field we tend to believe that most of our fantasies (sexual and otherwise) are kept safely beneath our own awareness.
As a Psychiatrist, I can tell you that quite normal people commonly contain all sorts of aberrant and "abnormal" fantasies which they would never act on or tell even their spouses about.
For what it's worth, Sexual fantasies: Are you normal?
Addendum, There Are Very Few 'Uncommon' Sexual Fantasies:
The study found that one of the most common sexual fantasies, after the five “typical” ones, is submission, with approximately 65 percent of women and 53 percent of men fantasizing about being submissive. More men than women fantasized about dominating their partners. Still, there remains a distinction between fantasy and reality. Of the women who fantasized about being dominated, half said that they wouldn’t want to actually be dominated in real life. Reading 50 Shades of Grey, for example, could be an outlet to imagine these fantasies without acting on them.