It can be anything. From its look, paintwork, engine performance, feel of the steering wheel, that deep deep dashboard holder etc. It is probably something very unique to your car make or model or maybe something you have added on yourself.
I ask this of my car owning friends and colleagues before I bought the Latio so that I can actually keep a lookout for these items before I sign on the dotted line.
I'll start first.
Mine is a Latio and the one thing I really really like is the ion cluster plasma aircon unit which comes with the car. Don't laugh ok. That thing really works and removes any bad smell from the car. The car still smell fresh and clean even after so many months.