Plug in this USB doll, set up your Skype, Yahoo or MSN client, and when your friends IM you, he hits himself on the head with a hammer. Feel free to tape a new face on him, so a relevant party receives the pain with each lolcat link that gets passed to you. You can also patch the i-Knock with custom MP3s to play for extra special IM-ers. [Stysen via Slippery Brick]
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I like the custom MP3 sound part, as my list is divided into 2 categories anyway: Friends group and the TimeOut/Penalty group, who are generally stalkers who are only on my list so that I can keep them stealthed and they NEVER know I am on line.