Mom and sister's panties
When I was a teen, I used to use my mother's and sister's panties to masturbate. Sometimes I would shoot my load into them and put them back in the drawer, hoping they would put them on with my cum between their legs.
I actually jerked off into my sister's thong when we were both recently visiting our parents. I blew my load right in the area that would be where her "sweet spot" would be. Then I put them back into her suitcase.