This Japanese alarm clock sure makes it in the list of the most annoying ones (see list below) available. The BanClock only shuts up when you insert a 500 or 100 Yen coin.

The design of the Banclock is actually very stylish: Simple and a touch of retro created through the use of old school LED digits.

If you feed the Banclock each morning with a 500 Yen coin you can save up 50,000 Yen until the piggy bank alarm clock becomes full.
With 100 Yen coins you only collect 15,000 Yen.

A BanClock sells for 5,985 Yen (~$50) in Japan.
More details and photos on AkihabaraNews and on the Rakuten shop (Japanese).

Most Annoying Alarm Clocks
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Flying Alarm Clock
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Clocky