One of the most interesting examples I have is "イケメン", which means good-looking man in Japanese. I knew this word from a Japanese TV show called 美男ですね (pronounced as Ikemen desu ne). So I automatically thought that the word "Ikemen" is equivalent to the Kanji "美男", and should be written in Hiragana as "いけめん". But I was not sure, since I know "美男" is pronounced as "びなん"...... Anyway I started to use this word when chatting with my Japanese friend online; however, to my surprise, they told me that the word should be written in Katakana not Hiragana. So I checked online, and I found "イケ" comes from the Japanese adjective "いけてる" (charming, handsome); "メン" is the same pronunciation as "man/men" in English, but can also be written as "面" in Kanji, which means "face". Yes, hot men have charming faces! I guess this word was probably firstly created as a joke...... And the reason for this word to be written in Katakana is mainly because it is a 流行語 (trendy word), and is usually meant to be emphasize in the context.
The second example is "オノ・ヨーコ", the famous Japanese born artist and musician. It is strange to me since both of her first name and last name are Japanese names, and should normally be written in Kanji as "小野洋子". However, in Japanese press and media the name was usually written in Katakana. And the first name is before the last name, which also follows the Western tradition. The possible reason for this might because of Ono's marriage to Lennon, which made her a foreigner's wife, and thus should also be considered as a foreigner. An other example for this is クリスティー・ヤマグチ(Kristi Yamaguchi), an American figure skater. Although her last name is obviously a Japanese last name (山口), yet the whole name is written in Katakana.In essence, most of the text books describe the usage of Katakana in three big categories: loan words, onomatopoeia and emphasis. The "Ono Yoko" example points out that the first category does not only includes words (and also names) that are made abroad and spelled in foreign language, but also includes those entities (or people) that become part of the foreign culture. The final category can be very tricky because it basically makes possible for any Japanese word to be written in Katakana when emphasis is needed. Also many trendy words which does not necessarily have foreign origins are also written in Katakana, so that they are emphasized and distinguished from words that are more commonly used.
