I didn't find anything in my last 240SX. It was owned by an older guy who was pretty meticulous about keeping the interior clean. I took the whole interior apart a couple times... nothing.
My S12 200SX had an air freshener in it that, every time I got into the car, smelled like I had a girl in the passenger seat. Hard to describe the smell, sort of perfumey, sort of soapy, sort of just... girly. I eventually had to get rid of it because I think I was falling in love with my car.
My Neon had a baby's winter boot, shards of a broken CD, and a couple toy cars under the seats. I also found half a pack of newports wedged between the seat and console, and a lot of goopy sticky soda residue behind the trim panel for the radio and HVAC.
I just know I'm going to find some weird stuff in my new 240SX. When I test drove it, it was full of random stuff - clothes, books, food, that sort of thing.