Well, you're going to have to. Of the three, two are "trailers" in the sense that they're mostly there to set the tone, while the third is not. That third is a live gameplay demonstration. Meaning you get to see somebody playing Fallout 3. Meaning you get to see, amongst other things, the combat system in action, with a human controlling it. Above you'll find the game's "teaser", while after the jump, the gameplay demo and a downright charming live-action trailer.