Every normal zombie has a 2% chance to drop a Loot Bag, every feral/radiated zombie has a 3% chance, and Demolishers have a whopping 30% chance (typo?). These are in entityclasses.xml:
<property name="LootDropProb" value="0.02"/> <!-- Whether it drops a loot bag on death or not. -->
<property name="LootDropEntityClass" value="EntityLootContainerRegular"/>
The 2nd line there shows that it drops another type of entity called "EntityLootContainerRegular" (for normal zombies). Other options are "EntityLootContainerStrong" (feral/radiated), and "EntityLootContainerBoss" (Demolishers). These container entities have their own sections in entityclasses.xml:
<entity_class name="EntityLootContainerRegular">
<property name="Prefab" value="Backpack"/>
<property name="IsEnemyEntity" value="false"/>
<property name="TimeStayAfterDeath" value="1200"/>
<property name="LootListOnDeath" value="70"/> <!-- used to determine container X/Y size -->
...other stuff...
</entity_class>
It's the LootListOnDeath parameter that determines what you might find in the bag. The values are 70 (Normal), 71 (Feral/Radiated), 73 (Boss), and 74 (Bandit; oooh
foreshadowing!). To figure out what the numbers correlate to we have to open loot.xml and scroll down to the <lootcontainer ...> entries, which look like this:
<lootcontainer id="70" count="1,3" size="6,3" ... loot_quality_template="qualBaseTemplate">
<item group="cannedfood" count="1,2" prob="13"/>
<item name="drinkJarBeer" count="1,3" prob="5"/>
<item name="drinkJarBoiledWater" count="1,4" prob="10"/>
<item group="books" prob="6"/>
<item group="brassResource" prob="6"/>
<item name="resourceForgedIron" count="2,10" prob="3"/>
<item name="resourceForgedSteel" count="2,10" prob="3"/>
<item group="tools" prob="6"/>
<item group="rareTools" prob="3"/>
...several others...
</lootcontainer>
For the normal zombie container you can see there is a mix of junk (water, brass) and better stuff (rare tools, forged steel). In general, even the normal zombie drop loot is better than, say, a random cabinet or desk, but a bit more broad than, say, a backpack found on the road (lootgroup name "backpacks/survival" in loot.xml if you care to check).
The loot container for feral/radiated zombies (id=71) is essentially the same as 70, but with probabilities changed so that 'better' stuff is a bit more likely. It also adds a couple of better loot categories to the choices.
The loot container for 'boss' zombies (Demolisher only, at the moment) is quite good, with the only mediocre stuff (depending on your priorities) possibly being vehicle parts and old cash. The rest of it is ammo, weapons, armor, books, medical, etc.
The Bandit group (id=74) has this:
<lootcontainer id="74" count="1,2">
<!-- bandit melee -->
<item group="banditsGeneral"/>
<item name="meleeClubWood" prob="0.7"/>
<!-- bandit ranged -->
<item group="banditsGeneral"/>
<item group="groupWeapons_Gunslinger" prob="0.7"/>
</lootcontainer>
The "banditsGeneral" loot group has food, heavy armor, face piercings, boiled water, clothes,
wait a minute go back a couple...face piercings? Hey, that's what it says...
Code:
<lootgroup name="banditsGeneral">
...
<item name="apparelFacialPiercings" prob="0.1"/>
...
</lootgroup>