The Joker's machine pistol was his main firearm.
During the robbery of Gotham National Bank, the Joker used a two-tone Glock 17 converted to full-auto to shoot the bank's manager.
He next used it to shoot his bus driver thug in the chest, killing him and leaving no witnesses.
He then used it to try and shoot through the SWAT truck in which Harvey Dent was in to attempt to kill him but was unsuccessful.
It is finally seen inside Harvey Dent's hospital room, as he shoots officer Jeremy Polk while crudely disguised as a nurse.
While in Dent's hospital room it had a suppressor on it.
- The Glock 17 the Joker uses was converted from semi-automatic to fully automatic with extended magazine, making it similar to the Glock 18.
- During the armored car chase, when the Joker fires the Glock 17 at the GCPD armored car, it can be seen that it jams after the first shot, but we see it still fire the rest of the magazine.
- Even though The Joker uses the Glock 17 one handed during the bank sequence, most Glock 17 and 18 owners recommend to hold it with both hands to keep the line of bullets steady and accurate. This is not surprising, however, as the Joker is known to have a lack of care for himself.