Everything so thank goodness we are currently renters.

I hate the small, tiny, useless for light and barely useful for air windows.
I hate showers over baths, and I hate toilets in bathrooms.
I hate that our kitchen doesn't have 'a place' for a fridge.
That the design of the living room ultimately requires a modular lounge to keep it tidy (ie no couches everywhere)
I hate the positioning of nearly every single power point and light switch.
The floorboards are unsealed, rotting, and retain no warmth in the house.

but, like i said, we're renting so I guess thank goodness that is the case.