Poke unresponsive people
Once Joanna Cave feature is implemented (https://microsoftteams.uservoice.com/forums/555103-public/suggestions/36769033-being-able-to-see-who-has-viewed-each-message-in-a) will be nice to get a 'poke' to which poke unresponsive users that have read the message but stubbornly ignore it.
Poke a user that is sleeping during a meeting
If I remember correctly lot of feature they had back in nineties in MSN messager are missing from Teams. e.g. emoticon addition and poking separately chat window etc.
Simon Jackson commented
Yes, a way to resend a notification about an existing message without creating a new message. A gentle poke - tap tap. Sometimes I get lost in multiple windows, so someone reminding me about a chat thread would be useful.