Send Whatsapp messages to anyone. Even if they are not in your contact list! Now with support for whatsapp for business
You just need to know the phone number, hit chat and your are into the conversation. Useful when you need to contact a buyer or a supplier.
Also, it's useful to hide your photo (and other privacy data) to the person you are chating with., just make sure to tune the Whatsapp settings > Account > Privacy to My contacts or Nobody