Minecraft death trap

first you need to find a flat surfaces so others can see, than make a 1x1 room with a 4 layer high 5 being the roof. put a piston in one of the wall in the 3rd layer and lava on the 4th layer leave the 2nd and the 1st layer empty for the player to get in. put a converter wired to the piston and the lever near the door (iron) to make sure that the victim is fooled because they cant see lava. now put a sign in your trap entrance with something like "get in for diamonds" your quiet done with this.

you can change the lava to water so they will die slowly. if you want to see them drown hide under a dirt and press the sneak button to stay hidden once you see a name move quiet slowly get out and enjoy the drowning player. to see it make a small window.

i prefered to choose water so when the player died we can gain their items and exp with another entrance under ground. but if the server have the plugin that can do the "/home" or the "/f home"
choose lava to take revenge.