I play on rotation and try to make each household use different things and live in different worlds, so it's quite difficult to say what I mostly use in gameplay. There are some BB and CAS items I do tend to repeatedly use though:
CAS - Cargo trousers from Moonlight Chic, the ones with pocket on one side and trainers from same kit (both for males and females), the female waistcoat from HSY, a tatty pair of jeans from Bowling, the tatty shorts from Werewolves, low trainers and jeans from Grunge Revival.
BB - Radiators! I love them now they can warm the rooms. Yoga mats (to keep slim) and bikes (for fun). Fun goes up SOOO fast on a bike! The 'typewriter' from Cottage Living and the little laptop from Strangerville. And the Super Subtle Saucer Light finds its way into every lot.
I wonder if anyone bothers to use the light switches we were given.