EntityLivingDeathDrops

The EntityLivingDeathDrops Event is fired whenver an Entity’s death causes dropped items to appear.
It can be canceled to stop the entity from dropping anything.

Event Class

You will need to cast the event in the function header as this class:
crafttweaker.event.EntityLivingDeathDropsEvent
You can, of course, also import the class before and use that name then.

Event interface extensions

PlayerDeathDrops Events implement the following interfaces and are able to call all of their methods/getters/setters as well:

ZenGetters

The following information can be retrieved from the event:

ZenGetter Return Type
player IPlayer
items List<IEntityItem>
damageSource IDamageSource
isRecentlyHit bool
lootingLevel int

Modifying the item drops

You can either add to the droplist or completely substitute it with a new one:

event.items = //reference to IEntityItem list.

//event.addItem(IItemStack item);
event.addItem(<minecraft:iron_ingot>);

//event.addItem(IEntityItem iten);
event.addItem(<minecraft:iron_ingot>.createEntityItem(event.player.world, event.player.position));