Here are our favourite 15.
1 - Send the same message to multiple people without them knowing
In the top left of the WhatsApp "Chats" screen there is a little-used feature called "Broadcast Lists". This lets you send the same message to multiple contacts at once without them knowing, a bit like the "Bcc" button on emails.
Rather than turning to Facebook to invite people to a party event, or asking multiple people if they want to play football without setting up a group chat, you can do it with one message in WhatsApp.
Go to Chats -> Broadcast Lists -> New List -> add contacts and write out your message -> hit send. The message and their reply will appear in your private chat with each person, but with a little megaphone icon next to it. Your contacts won't have any idea that the message was sent to anyone but them.
2 - Bold, Italics,
You can format the text in WhatsApp messages by adding symbols in front of and after words.
1 - For bold add asterisks to either side of a word or sentence, e.g. *bold*
2 - Italicise a message with underscores, e.g. _italics_
3 - To strikethrough text add tildes, e.g. ~strikethrough~
You can also combine the formats by adding multiple symbols before and after a word, such as _*bolditalics*_.
3 - Find out who you talk to the most
To find out who your best friends on WhatsApp are, if you have an iOS device, head to Settings -> Account -> Storage Usage. Here you'll see a list of the people and groups you message on WhatsApp along with the total number of interactions you've had with that person/group.
If you select "Size" at the bottom right of the screen you can see who you have spent the most data WhatsApp-ing.