Always first-person. I could care less about look at the model I'm controlling, and third-person shooters are often hard to aim with because of the character taking up a generous amount of the screen. Atmosphere-wise, first-person wins again. From a first-person view, it's much more immersive because I feel like I'm actually there.
EDIT:
Does anyone even know what second-person is?
---
Definition: In second person point of view, the narrator tells the story to another character using "you," so that the story is being told through the addressee's point of view. Second person is the least commonly used POV in fiction, though there are a few examples. Many of the stories in Lorrie Moore's book "Self-Help" are written in the second person, as is Tom Robbins's "Half Asleep in Frog Pajamas," which begins: "The day the stock market falls out of bed and breaks its back is the worst day of your life. Or so you think. It isn't the worst day of your life, but you think it is." source
Think of a text adventure. (It is pitch black. You are likely to be eaten by a Grue.)
Examples: Choose Your Own Adventure Books are told from the second person point of view, as are many computer games. source
Again, text adventure games. The Choose-Your-Own-Adventure example should be self-explanatory.