Han-ji: Taiwanese written with Chinese characters
Using only characters in writing Taiwanese means that alternative glyphs must be found for syllables with no Mandarin equivalent. Sometimes these are found in ancient Chinese writing that has fallen in to disuse, and sometimes the characters are invented by taking a character with similar pronunciation and adding an extra element to it. The drawback of this method is twofold - firstly, the necessary characters are usually not encoded in Unicode, meaning that it can be almost impossible to use them on a computer. Secondly, and far more seriously, there is no universally recognized scheme in place to standardize these characters, meaning that they are often ad-hoc and limited to the person who invented them. Taiwan's Ministry of Education has recently released a list of 300 standardized Han-ji words for Taiwanese (PDF), but a complete, widely accepted system is still only a distant possibility.
