Valorant is an FPS developed by Riot Games. You play as one of eleven available characters, each with four unique abilities. The last agent implanted in-game was Reyna, who's a pretty good fit for an aggressive player.
At the time of beta, the publisher had indicated that the game would come with twelve agents, which is still not the case. This is why many players try to search for information and clues. Several things go in the direction of a hidden agent named Killjoy or Bombshell.
One of the rewards of the Ignition Battle Pass is a card showing a turret, on which is marked "Vertraulich" (confidential, in German). One could then easily suppose that the 12th agent will come from Germany and that he will have this turret in his kit, as specified by PlayerIGN.
Floxay has also made a prototype animation of the turret. He also stated that he didn't know whether it was controlled by the player directly or automatically.
However during the beta, another capability had been discovered by PlayerIGN: Killjoy/Bombshell would also own a drone.
For the moment, no information has been revealed by Riot Games regarding future agents. Between these clues and those given by Morello, it's certain that several agents are in development or have been abandoned along the way.