A New World - S3-E20
Corrected entry: Connor's stake cannon has 3 barrels, all of which are assumed to be loaded, when he arrives. During the episode teaser, he fires one stake from each of the three barrels. After the credits, he fires two more stakes from the top barrel and one from the right. Of course, he hasn't stopped to reload and it's obvious that there is no room in the simple device for more than a single projectile and the launching mechanism. (00:00:15 - 00:01:50)
Correction: The shot is off Connor for a long time after he fires the first stake (as it follows the stake across the room and shows Groo and Gunn starting to charge) and Connor can move at incredibly fast speeds, so it's possible he reloaded the device during that space of time, which would explain why 4 stakes are fired from a device that only holds three.
Shay