21. Sex toys, for obvious reasons. However, just because that hacker guy next door always working on his startup has them lying around for the right occasion, it doesn't mean they have ever actually been used. Not to worry though, hackers can't get a date? There's an app for that. ;)
Toilet paper. May contain excrements of the previous user,
source of bacteria and diseases.
Cars. May have been dropped, neglected, may have bacteria and mites inside. Besides it usually has used tires and used car seats.
Used laptops are fine as long as they are still under the manufacturers warranty.