Holy crap, that looks so freakin awesome.
The head looked almost real.
The city looked so good, the flames were fantastic.
The energy balls (or whatever) form the gun looked amazing, great physics too!
The moving plants when the child was running through was done spectacularly, the Sandbox UI looks really good too. The waterfall in the editor was great too, haven't seen a game with water physics as good as that.
The sandbox style of play with destructible environment looks like it'd be thrilling, blowing up a great arch. Making debris and trees fly all over the place from an explosion set off far far away, that is wonderful.
CryTek have done wonderful with the engine and with that HD Trailer. They are the masters of gaming.