We've introduced Internal Notes for Conversations and Mentions for both Tickets and Conversations. You can add an internal note, use an "@" sign, and pick an Agent you want to mention.
The mentioned person will see the mention inside a dedicated folder in the Inbox, and can also receive web and email notifications.
Using mentions can be helpful when you want to:
Get help from other people.
Push a ticket to a different Agent, but want to make a quick intro.
As an Admin, give advice or training.