The drug needs to make the taker (who is unaware of ingestion) suggestable and kind of removed from his/her usual chain of thought, so that if something that seems out of character or out of their normal morals is suggested to them, they'd go along with it without thinking through the consequences. But I need it not to knock the person out (which I'm thinking eliminates the obvious choices of rohypnol and GHB, though I've found little information on what these do in small doses), though it could include short-term memory loss. It could be a designer drug, but one that's not uncommon in a club or rave scene.
I was thinking ecstacy, but from the research I've been able to do on it, it seems to more increase the dopamine levels (thus feelings of euphoria) than increase suggestibility. I've also seen a ketamine-cocaine come up a few times, but I don't know much about this combination and it seems like too hard a combination to master to slip into someone's drink.
Information on the person who's going to be ingesting: athletic young male (about 22 or 23), 6 feet and around 180, fairly good tolerence for alcohol.
Any help is appreciated!