A long QSO between two amateur radio operators. This is generally what amateur radio operators are doing on the radio when they're not contesting, testing equipment, bouncing signals off the moon or meteor showers, providing communications in national emergencies, sending still or moving pictures or text back and forth, connecting to packet radio networks, and partaking in nets.
Nice chewing rag with you, catch you later down the log.
The most famous phreak of all time, who discovered that the whistles that came in boxes of Captain Crunch cereal emitted perfect 2600 Hz tones. 2600Hz was the frequency used by Bell's switching systems to indicate a trunk being freed. By sending 2600Hz after making a call to a WATs line after they hung up, you could trick the phone network into giving you another dial tone, on which you are not charged. You could then send MF tones to dial your second (free) call. Steve Wozniac, co-founder of apple computer supposedly used this trick to prank the pope without paying anything or being at all traceable. None of this stuff works anymore, of course.
Captain Crunch whistles are now sold out of the back of 2600 magazines for $99. But they don't actually do anything anymore.