where else are there timezone increments of other one hour?

Max,

I can only speak with authority for the Australian locations South Australia (Adelaide) and Northern Territory (Darwin), both GMT +9:30, but judging from the choices I get when I make a custom change to my Windows clock or your handy clockrack (I think the list I see is courtesy of Mr Gates), there are also the following:

GMT -3:30 Newfoundland
GMT +3:30 Tehran
GMT +4:30 Kabul
GMT +5:30 Bombay, Calcutta, Madras, New Delhi

Agrees with the list at http://time.greenwich2000.com/info/time-now.htm

Note the Chatham Islands don't appear on either.

The Greenwich site refers to "standard" time zones which differ from GMT by an integer number of hours.