Leaving oily fingerprints when car is clean. (especially windows)
Putting objects on car that will scratch paint.
Hitting my car panels. (Had a kid relative kick my door panel just because when he tried opening my door and it was locked. Left me a dent.
)
People I take to the beach and make my car all sandy. (the floor I don't mind, but my seats?! Heck naw!
)