As far as teasers go, the new Fallout New Vegas trailer (after the break) looks tasty. Infinity Ward and Ubisoft who both released dire teasers last year with Modern Warfare 2 and Assassin Creed 2 respectively, take note of what Bethesda have done here..
The old zoom out trick. Worked also too with Bioshock 2 Sea of Dreams teaser a few months ago. It would be extra nice if they showed game play though like they used to in video game ads. We are too forgiving these days with teasers and should demand stuff like the guns, the achievements, the level cap, any collectibles, the achievements, the armour and of course the DLC achievements. Then we would be impressed.