Oxford English is surely the most 'fun' because they differentiate between -ize and -ise suffixes based on the origin of the word (greek vs. latin/french IIRC). Though as far as I know, most British have standardised on the -ise suffix. In Australia we have definitely standardised on -ise, hence my own spelling. While Americans standardised on -ize.

None the less, I undertook one semester of commercial law at university a while ago and had to learn Oxford spelling for the exam as it is apparently used in our legal system. This is despite the fact that the government's own style guide standardises on -ise.