it's usually the AI that gives you these wow moments when it has matured enough.
It doesn't even have to be all that mature, although yeah, I get this moment the most due to AI. Most recently, I separately developed the random movements, the flaming breath, and the speech balloons for characters in Flamewar! When I brought the elements together and saw them all together for the first time, it was definitely a startling experience. The characters weren't even reacting to the player yet; it was amazing just to watch them randomly milling about, shouting and breathing flames.
Other than AI behaviors, nothing is ever surprising because you slaved over it every step of the way. As cool as it may be to somebody seeing it for the first time, your main character (say) has gotten pretty tiresome by the time you're finished modeling, texturing, and animating him.