The 8 types of kills you can get are: Sword, Trap, Poison, Water, Explosive, Tiger-Trap, Spike, and Fall.
Buy about 8 bamboo traps from the shop. Set them up in a line and lure an enemy into the first trap. He should bounce on each trap you set, dropping some kind of item with each hit. You can then sell those items as well as your eight trap kills at the shop.
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