In our campaign, the guy packing the heat is Ispher, but really it works for anybody with a penchant for shooting and at least 4 fatigue:
Weapon: Ripper
Items: Gauntlets (the ones that allow fatigue recovery on a surge), and Archer's Charm
Skills: Master Archer, Rapid Fire, Eagle Eye
Oh, and: 2 ranged upgrades for a total of 4 black dice in shooting.
In this combo, from full fatigue against enemies up to 6 squares away, he got off around 20 shots and stopped only because he had run out of targets (in the graveyard, no less. Our OL was mightily hacked)
Mathwise: two free surges from master archer guarantee a fatigue point, and 7 dice being rolled average out at least another 2. The combined Pierce of the combo is 5 (from the Ripper, Eagle Eye, and the Charm). Short of rolling a miss, and the Ripper allows the reroll of a single die, so a series of misses, it is highly improbable that this combo will not kill everything within LOS and 6-8 spaces.
Even as a player, this is overkill.......
As a solution, we have instigated this house rule: The number of bonus shots that may be taken in a single action is limited to the base number of Fatigue points the character has (in this case, 4). This seems to work reasonably well, since the rest of us were feeling left out of the action while Ispher dominated the scene (with his snazzy Van Helsing crossbow)