Zynga added a feature to tell us what loot is rare, common and uncommon (1). I figure this is as good of time as any to determine what is considered rare by doing some drop rate studies.
Fighting High End Loot
Las Vegas Loot
Chop Shop, Weapons Depot and Armory
Here are the items that one can expect to get while doing job in Italy.
Here are the results of a 5,000 job run in Region 5 on the Ruby Level. Use the same equation above to figure out the drop rate except use the total energy spent as the denominator. For example, the Meadow Viper and the Corpo Armatura are the only two loot items that are in the Top 8 for maxing out your equipment scores. During the run below 685,000 energy was spent (137 X 5,000 Jobs) and 32 of these items dropped (21 + 11). 32/685,000 = 0.0000467 which is 0.0047%. These numbers sure don't motivate me to even have a hope of gaining 501 for my main account. The drop rate for building parts isn't that great either (0.03%). At least we can use the free gifts and help each other out with those.
Here are some of the Las Vegas items that drop while doing jobs.
Its been a while since I checked on the drop rates in Las Vegas. Below is a 5,000 job run and once again the drop rate isn't very promising. In District 8, 4 of the Top 8 Giftable items drop (Arcturion Assault Rifle, Cooling Vest, Ballista Missle Launcher and the Bighorn). 790,000 energy was used (158 X 5,000) and 105 of these items dropped giving a 0.013% drop rate. I'll agree with Zynga that these items are rare.
I'm often asked why my main account isn't maxed on Lad Vegas loot. I have this great big energy account but unfortunately its banned from gifting and fighting. I haven't contacted Customer Support to get the ban lifted because it's an energy account and not in my name. I get a lot of use from the account doing drop rate studies so I'm not overly concerned about it.