Irene/Sherlock or Ian Sherlock... though technically they should work out to the same thing.... I think...
Let’s say Irene, for the sake of clarity.
who is the big spoon/little spoon: Irene is always the big spoon—actually, no, there’s one (platonic) exception, but Sherlock isn’t it.
what is their favorite non-sexual activity: Talking. Just talking. The room sparks when they really get going.
who uses all the hot water in the morning: It’s always a fight to the death. Irene punishes Sherlock if he uses it all up, though, so Sherlock makes a point of doing so.
what they order from take out: Chinese, still. But Irene doesn’t like takeout. She’d rather make Sherlock cook.
what is the most trivial thing they fight over: Sherlock’s sleeping habits.
who does most of the cleaning: Kate.
what has a season pass in their DVR: See response below.
who leaves their stuff around: Sherlock.
who remembers to buy the milk: Still Kate, that poor girl.
who remembers anniversaries: Again, both of them are surprisingly okay about this.