Quicksmith Rebel

The trick here is that the gun and the bullet are different objects. The body grafts a Goblin Sharpshooter style pinging ability onto an artifact you already control, which means the artifact becomes the threat and this 3/2 becomes the conditional license that keeps it firing. Point it at a sacrifice-fodder mana rock or any cheap artifact that was doing nothing offensive, and you have welded repeatable removal onto a permanent that had no business attacking. The duration clause is the load-bearing restriction: it ties the gun's life to the Artificer's, so a single removal spell on the 3/2 turns the armed artifact inert no matter how long it has been firing. That dependency also means each Rebel weaponizes exactly one target at a time, and only that target; arming a second artifact requires a second instance of the trigger, since the enters ability points at one artifact and the granted ability on the first ends the moment the creature leaves. The damage reaches any target, so the gun doubles as reach to the face or a way to chip a planeswalker, though the strength is grinding tap-down control rather than a burst. What the conversion buys is the real prize: an artifact's tap symbol becomes a recurring instant-speed source of two damage, and instant-speed pinging from an untapped permanent is far harder to play around than a sorcery-speed shock.