Yes, you read that correctly, you can watch an ASCII version of the full Star Wars Episode IV movie right in the Command Prompt window!
Star Wars Screenshot
Just open Command Prompt and execute telnet towel.blinkenlights.nl. The movie will start immediately. This isn't a terribly productive use of the Command Prompt, nor is it really a trick of the Command Prompt or any command, but it sure is fun!
Note: The telnet command is not enabled by default in Windows 7 or Windows Vista but can be turned on by enabling Telnet Client from Windows Features in the Programs and Features applet in Control Panel.