Hey everyone!  I spearedyou's back and i've done some extensive research and expirements. 
I have come up with this cool result.  The subject is: NPCs Freemies and Several Members-
What they are weak against, and what they drop, and how commonly the items appear.  Please
note that the more you kill a certain monster, the more awesome items it can give you. 
Also note: try expirementing with the same monsters, just different levels.


Chart Start:

Man-Weak against: Slash attacks
Drops-
Bones-Always
Coins- Very Common
Fishing Bait-Rare
Bronze Arrows-Uncommon
Bronze Medium Helmet-Rare
Herbs (members)-Common

Woman-Weak against: Slash Attacks
Drops-
Bones-Always
Coins-Very Common

Mugger-weak against Slash Attacks
Drops-
Bones-Always
Coins-Common
Rope-Very Common
Herbs (Member)-Common

Goblin-weak against Slash Attacks, Chop Attacks  (sometimes), Magic Attacks
Drops-
Bones-Always
Coins-Very Common
Bronze Square Shields-Uncommon
Body Runes-Rare
Water Runes-Uncommon
Goblin Mail-Common
Bronze Full Helmets-Common
Bronze Arrows-Uncommon

Cow & Cow Calves-weak against Chop attacks
Drops-
Cowhide-Always
Bones-Always
Raw Beef-Always

Chicken-Weak against Chop Attacks, Magic Attacks
Drops-
Feathers-Very Common
Bones-Always
Raw Chicken-Always

Farmer-Weak against Slash Attacks, MAgic Attacks
Drops-
Chaos Runes-Very rare
Bones-Always
Seeds of some sorts (member)-Common
Rake (member)-Uncommon
Coins-Very Common

Imp-Weak against Slash Attacks, Chop Attacks, MAgic Attacks
Drops-
Ashes-Always
Wizard Hat (Blue)-Random
Bronze Crossbow Bolts-Random
Bucket-Random
Wheat-Random
Yellow Bead-Random
Red Bead-Random
White Bead-Random
Black Bead-Random

Minotaur-Weak Against Chop Attacks, Slash Attacks, Magic Attacks
Drops-
Bones-Always
Coins-Very Common
Iron Arrows-Very Common
Bronze Full Helmmets-Common
Uncut Sapphire-Rare
Uncut Emerald-Very Rare

Giant Rat-weak against Chop Attacks
Drops-
Bones-Always
Raw Rat Meat-Always

Rat-Weak against Chop Attacks, Slash Attacks, Crush Attacks
Drops-
Bones-Always
Rat Tail-Always

Zombie-weak against Slash Attacks, Magic Attacks (Especially Crumble Undead)
Drops-
Bones-Always
Coins-Very Common
Mithril Arrows-Uncommon

Guards-Weak against SLash Attacks, Crush Attacks, Magic Attacks
Drops-
Bones-Always
Coins-Very Common
Potato Seeds (member)-Common
Iron Dagger-Uncommon

Wizard-Weak Against Ranging, Slash Attacks
Drops-
Bones-Always
Mind Runes-Common
Air Runes-Common
Wizard Robe-Uncommon
Wizard Hat (Blue)-Uncommon
Coins-Common

Dark Wizard-Weak Against Ranging, Slash Attacks
Drops-
Bones-Always
Coins-Common
Chaos Runes-Uncommon
Law Runes-Rare
Wizard Hat (Black)-Uncommon

White Knights-Weak Against Crush Attacks, Slash Attacks, MAgic Attacks
Drops-
Bones-Always
Coins-Common
Pot Of Flour-Rare
Mithril Arrows-Common

Black Knights-Weak against Magic Attacks, Crush Attacks, Slash Attacks
Drops-
Bones-Always
Coins-Common

Dark Warriors-Weak Against Magic Attacks, Slash Attacks, Crush Attacks
Drops-
Bones-Always
Coins-Common
Nature Runes-Rare
Black Mace-Uncommon

Wolf-Weak Against Chop Attacks, Slash Attacks
Drops-
Nothing- Just good for gaining XP

Spider-Weak Against Chop Attacks, Crush Attacks
Drops-
Nothing-Don't even bother training on them

Giant Spider-Weak Against Chop Attacks, Crush Attacks
Drops-
Nothing-Don't even bother training on them

Druids(Member)-Weak Against Slash Attacks, Ranging
Drops-
Bones-Always
Coins-Common

Ogres(Member)-Weak Against Slash Attacks, Magic Attacks
Drops-
Big Bones-Always
Coins-Common
Wierd Seeds-Common

Hill Giants-Weak Against Slash Attacks, Magic Attacks
Drops-
Big Bones-Always
Coins-Common
Iron Full Helms-Common
Steel Arrows-Uncommon
Steel Swords-Uncommon

Barbarians-Weak against Slash Attacks, Magic Attacks, Ranging
Drops-
Bones-Always
Coins-Very Common
Chaos Runes-Rare
Law Runes-Very rare
Bronze Woodcutting Axe-Uncommon
Staff-Uncommon
Tin Ore-Uncommon
Bear Fur-Uncommon

Skeleton-Weak Against Slash Attacks, Crush Attacks, Magic Attacks
Drops-
Bones-Always (Hey, they're Skeletons!)
Coins- Very Common

Gunther The Great-Weak Against Slash Attacks, Crush Attacks, MAgic Attacks
Drops-
Bones-Always
Coins-Common
Iron Woodcutting Axe-Uncommon

Lesser Demon-Weak Against Slash Attacks, Magic Attacks
Drops-
Rune Chainbodies (That's the rumor around some places.  I suggest you don't trust it with
all you have)
Rune Medium Helmet-Rare
Ashes-Always
Coins (Large Amount)-Common

Rock Golem-Weak Against Crush Attacks, Magic Attacks I think
Drops-
Dwarven Stout-Random
Beer-Random
Earth Runes-Random
Bronze Bar-Random

Tree Spirit-Weak Against Slash I think, Magic I think, Crush Attacks
Drops-
Nature Runes (Another silly rumor.  But who knows?)
Scyth (An even crazier rumor!)
Uncut Sapphire-Random

Market Guard(members)-Weak Against Slash Attacks, Crush Attacks, Magic Attacks
Drops-
So far I haven't experienced or seen the items that Market Guards drop

Scorpion-Weak Against Crush Attacks, Slash Attacks, Magic Attacks, Ranging
Drops-
Nothing-Just good for XP

Al-Kharid Warrior-Weak Against Crush Attacks, Slash Attacks, Ranging, Magic Attacks
Drops-
Cabbage-Uncommon
Bones-ALways
Coins-Common
Herbs (members)-Common
Copper Ore-Uncommon

Bears-Weak Against Chop Attacks, Slash Attacks
Drops-
Bones-Always
Raw Bear Meat-Always
Bear Fur-Always

Well, that's it for now!  If you have any questions, contact me on Runescape. 
I_Spearedyou's the name.

P.S. If you are interested, you can join the all-growing clan that Dragonjaw100, Alder__11
and I are running.  We're getting more members each day, but be assured: We may need
you!!!!!!!