Every time you change your toilet tissue roll in your bathroom, add a few drops (or more than a few if your bathroom is large) of essential oil to the middle of it and it will keep the room smelling lovely.
add baking soda to your litter box and it won't smell. I have two litterbox's in my home in plane view and people don't know they are there because they can't smell them. I also have the litterboxs facing the wall to give my cat privacy and I don't want to see my cat do it's business.