The 45 Shepherd is a powerful handgun in Saints Row: The Third. The name suggests that it is the successor of the .44 Shepherd, though visually it is more similar to the GDHC .50. A "brute force" firearm first and foremost, the Shepherd is favored by the various gangs in Steelport due to its flexibility and raw punch.
The Shepherd is a powerful, accurate, slow-firing firearm that is much more potent per-shot and much more accurate (at first) than the KA-1 Kobra favored by law enforcement. By default it holds 8 rounds, and its heavy barrel ensures that it's extremely accurate. Unfortunately, it has a sluggish rate of fire (dual wielding and upgrades both alleviate this) and a harsh kick, which means that using it at long-range involves taking your time and aiming it to get the most out of it, as opposed to filling the air with lead.
Upgrades only make this fierce pistol more so. The level 2 upgrade improves its rate of fire, with the level 3 increasing clip size to 14. The level 4 upgrade gives the Shepherd explosive rounds, which not only have additional punch, but which can send enemies flying through the air or damage multiple foes at once. Unfortunately, the rounds do not discriminate - they are quite capable of causing damage to allied units if fired carelessly, and can even harm the user if they're fired up close.