Minecraft wiki entry for Traps, associated text: Use shears to collect spider webs. Then dig a 3 block deep hole placing lava at the bottom and cobwebs on the top layer. Anyone not watching their step could get caught in the web and slowly fall to their death, allowing you to get a few dramatic words in as they die. (experienced players will be able to get out of this by mining the cobweb, and quickly placing a block in the lava)