I find the phenomenon of ‘pickup artists‘ somewhat disturbing.
Basically, these are individuals who exploit quirks of human psychology in order to get people to sleep with them easily. Human behaviour is predictable to such an extent that many tricks are effective against a sizable proportion of the population. For example, you can use a minor insult called a ‘neg’ to make a person feel like they have to prove themselves to you. A long piece on pickup artists in The Point Magazine describes how this is at the core of the technique: “the key to the method is, unquestionably, that the pickup artist ignore, tease, or even insult the targeted female, accustomed as she is to constant, beleaguering attention from men.” There is also the whole collection of cold reading tricks long employed by psychics and con artists to give the false sense that they have special insight into you.
If people were widely aware that such tricks can be effective, the practice of people using them would be less worrisome. When they are employed against unwitting subjects, however, they strike me as exploitative and potentially unethical. The article linked above contains a detailed discussion of the ethics and psychology of this unusual set of skills.