Well, coming from someone who thinks its all subjective... at the same time, I believe the quantity of different styles, sounds and such have an effect on that and how they're achieved, so... probably drums. That's including every possibility, considering you can do such a wide range of techniques and have such a wide range of drums in type, size and tuning.
Not so much, Christmas depresses me.
Nope.
Do you like yoghurt?