I don't like making tut's but, I saw a guy requested it so here 
CREDS:everyone
open item2.java
find
(beginning of the java file
)
and paste this under it
Code:
public static int Mithdrag[] = {4151,1053};//change these drops!
public static int randomMithdrag()//change the name to whatever
{
return mithdrag[(int)(Math.random()*Mithdrag.length)];
}
(this says that when called upon drop either a whip(4151) or green mask(1053)
To edit this simply change the item numbers to what you want, seperated by comma's
Save and open Npchander.java
next find
Code:
if(npcs[NPCID] != null && server.playerHandler.players[Play] != null && server.playerHandler.players[GetNpcKiller(NPCID)] != null) {
paste under that
Code:
if(npcs[NPCID].npcType == 3000) {// change me to your npc id
ItemHandler.addItem(Item2.randomMithdrag(), npcs[NPCID].absX, npcs[NPCID].absY, 1, GetNpcKiller(NPCID), false);
}
(this just makes it so when the npc that is 3000 is killed
now save compile, kill your npc and see if it drops. Have a good day