Apologies for the late post...

I was going to defend my earlier posts, but I've decided to come up with new katakana words that seem to be more interesting, and that go beyond the "textbook definition."

ヒフ科
One word that I have found is  ヒフ科, hifu-ka, which means "dermatology."

The first two characters are in katakana and the third one is a kanji. Indeed, here we have an interesting combination of kanji and katakana, when the katakana word is also a Japanese word, hence not a loan word. Here is the site that I've stumbled upon hifu-ka: http://www.hibiya-skin.com/

"Hibiya-Skin" is a clinic for dermatology (ヒフ科クリニック). What attracted my attention in this word is that ヒフ is indeed the Japanese word for skin, written as 皮膚 in Kanji. Trying to find out why a Japanese word was written in Katakana, I've ended up searching the word in the "best encyclopedia ever" - Wikipedia. Even though, the wiki page does not give a footnote, it states that it is commonplace to use Katakana instead of difficult Kanji used to express medical words (such as 皮膚).

Thus, here we have an interesting Katakana word.

And, here is the second one:

ドンマイ
Since I believe that languages are basically tools for communication, I will confess that I did not really find any place that officially employed this word (such as a newspaper, website, magazine, etc.). Instead, this is a word that a Japanese friend of mine told me. It seemed interesting and funny, because it is a weird loan word.

ドンマイ means "Don't mind!"
The interesting thing with this katakana is that it is not a loan word but a loan phrase. One Japanese friend of mine told me that it is usually the elder people saying ドンマイ to younger ones, whereas another of my Japanese friends said it was commonly used. I guess usage differs from region to region.

Having googled the word, there are of course thousands of results which can be read as a testimony to the contemporary usage of the word.