In Mafia Wars Las Vegas, the loot system is a little bit different. All of the new armor, weapon, animal, and vehicle pieces drop randomly from jobs in each district.
In other words, there is a set of about 5-10 items (I will refer to this as the "loot pool" for ease of reference), and by doing any job you randomly have a chance to get any of those 5-10 items.
With that said, here are the loot pools for each district (big thanks to Steven for putting this together!):
Moving Truck (vehicle; 12 attack, 20 defense)
Carver (weapon; 24 attack, 16 defense)
24k Chainsaw (weapon; 29 attack, 15 defense)
Football Jersey (armor; 10 attack, 28 defense)
Sand Storm (vehicle; 29 attack, 15 defense)
Bison (animal; 23 attack, 40 defense)
Road Tractor (vehicle; 25 attack, 33 defense)
Highrise Sport (vehicle; 29 attack, 38 defense)
Reinforced Boots (armor; 27 attack, 19 defense)
El Escorpion (armor; 40 attack, 30 defense)
Reinforced Tuxedo (armor; 28 attack, 34 defense)
Biohazard (weapon; 18 attack, 28 defense)
Pump Shotgun (weapon; 32 attack, 22 defense)
Classic Convertible (armor; 30 attack, 35 defense)
Motorcycle Helmet (armor; 22 attack, 32 defense)
El Escorpion (weapon; 40 attack, 30 defense)
Two Pair (weapon; 31 attack, 44 defense)
High Society (vehicle; 37 attack, 29 defense)
Femme Fatale (armor; 45 attack, 28 defense)
Ventilated Blast Cap (armor; 32 attack, 24 defense)
Belt Fed Shotgun (weapon; 27 attack, 36 defense)
Hard Four (vehicle; 30 attack, 50 defense)
Bark Scorpion (animal; 50 attack, 30 defense)
Dune Buggy (vehicle; 41 attack, 35 defense)
Set of Biker Leathers (armor; 30 attack, 48 defense)
Bighorn Ram (animal; 37 attack, 42 defense)
Precision SMG (weapon; 42 attack, 30 defense)
Range Finder Rifle (weapon; 37 attack, 54 defense)
Mojave Mike (vehicle; 40 attack, 53 defense)
I think this list is incomplete; if you have anything to add, please post in the comments. The best three pieces I have seen so far are the Bark Scorpion (animal; 50 attack, 30 defense), the Range Finder Rifle (weapon; 37 attack, 54 defense) and the Mojave Mike (vehicle; 40 attack, 53 defense).
I have seen the Bark Scorpion in District 4 and the Mojave Mike and Range Finder Rifle randomly in District 5. Players are claiming to have found pieces in all cities, but I have not been able to confirm this or noticed this myself. Anyone have any pictures?
Mafia Wars Las Vegas is also now live for all players!