In the film Prometheus, the android David does something that I'm unclear on:
After David examines the black liquid that he brought back to the ship, he poisons Dr. Holloway with a little bit of it.
What is his intention?
David's intention is to fulfill his master's orders and speed any developments that will lead to full contact with any alien intelligence. David's old Waylan master, Peter Weyland, wants to save his own life, but he has a diminishing amount of time to do that in. If infecting a crew member will help speed understanding of what they are dealing with, then sacrifices have to be made.
Peter Weyland is following an all-or-nothing strategy of taking whatever risks are necessary for extending his life.
Re comments: I don't think David knows exactly what's going to happen when the bioweapon gel is introduced to a human, but David has a fair idea that "something" will happen. Either way, David is simply following orders, in my opinion, fulfilling Peter's wishes to the letter. David seems to consider Peter to be his true father and seeks recognition from him.
Perhaps Peter reasons that by infecting Dr. Holloway with the fluid, the fluid may turn Dr. Holloway into another being, or provide some kind of biokey or some insight into what to do next, in order to make contact. The fluid could also be of some medical utility which Peter is very interested in.
From io9's interview with the cast and crew of Prometheus, screenwriter Damon Lindelof says:
In the scene preceding him doing that, he is talking to Weyland (although we don't know it at the time) and he's telling Weyland that this is a bust. That they haven't found anything on this mission other than the stuff in the vials. And Weyland presumably says to him, "Well, what's in the vials?" And David would say, "I'm not entirely sure, we'll have to run some experiments." And Weyland would say, "What would happen if you put it in inside a person?" And David would say, "I don't know, I'll go find out." He doesn't know that he's poisoning Holloway, he asks Holloway, "What would you be willing to do to get the answers to your questions?" Holloway says, "Anything and everything." And that basically overrides whatever ethical programming David is mandated by, [allowing him] to spike his drink.