Peyton Riley

"One machine gun belonging to Peyton Riley AKA the Ventriloquist. Or maybe the gun belongs to the puppet? I never really understood what's going on there."

- Aaron Cash's audio file.

Peyton 'Sugar' Riley AKA the Ventriloquist is a super-criminal. She is the second-in-command to Scarface.

Before Arkham Knight Incident
After the events of Batman: Arkham City, the original Ventriloquist Arnold Wesker was no-longer Scarface's second-in-command. The reasoning behind Arnold's disappearance is unknown as he wasn't arrested and incarcerated in Arkham City, something known due to a GCPD during the game stating that he at some point in the night robbed a bank. Whatever the reasoning, Peyton Riley became the new Ventriloquist and eventually fell into the sea where it was initially believed that both she and Scarface had met her end. Scarface, however, later resurfaced in the hands of Joker.

At some point, her tommy-gun was misplaced, causing it to be sent to the Evidence Locker of the GCPD building.

Arkham Knight Incident
During Arkham Knight, her Tommy-Gun is on display in the GCPD Evidence Locker.

Trivia

 * While her background and personality in the Arkhamverse is a little vague, in the original comics Peyton Riley was the daughter of a notorious Irish mob boss named Sean Riley. Peyton grew up being seen as nothing but a mafia-princess and was forced into arranged engagements by her father, one of which left her with a violent fiancee who blinded her in one eye. She eventually came into possession of Scarface after Arnold Wesker was assassinated under orders of the Great White Shark as part of a gang-war.
 * In the comics, Peyton was Scarface's lover as well as 2nd in command. Whether this is still true in the Arkhamverse is unknown.
 * Also in the comics, Peyton was once engaged to Dr. Thomas Elliot AKA Hush.