I still remember about 20 years ago a female friend told me that she masturbated using a bottle of Bawls energy drink (IDK if they even still make the stuff). It was a glass bottle that was bumpy all over (think of the divots on a golf ball, but inverse) and she apparently used it on her clit/vulva.

When I was a horny pre-teen boy and had no idea how to actually beat off, I discovered that rubbing a silk/nylon pillow with pictures of cats on it felt really good.