Before researching Katakana on the internet, I wasn't aware that Katakana can have so many more usages in addition to foreign words.

Here is some strange Katakana words I found:

• zabon ズボン – Trousers (or for you Americans who can seem to distinguish between underwear and trousers, I guess you’d call them pants).
• pinpon ピンポン – Ping-Pong! The sound of a doorbell.
• chuu チョウ – Very/Super/Extra – an emphatic word.
• homusapiensu ホモ・サピエンス – Homo Sapiens. 
• wanpeesu ワンピース – A one-piece dress. Two words combined.
• pasocon パソコン – A PC (personal computer). Two words combined and shortened into a classic 4-syllable marvel.

The Katakana expressions above are 4-syllable words, usually combined by two words. 

• toranpu トランプ – Cards (Trump cards).
• baikingu バイキング – Oh-ho. Those dastardly Vikings. But no, this means an ‘all-you-can-eat’ restaurant.
• manto マント – A cloak or a cape. 
• manshon マンション – An upper-market apartment. Not a mansion.
• anke-to アンケート – A questionnaire!
• hocchikisu ホッチキス – A…hot kiss? Hah, you wouldn’t want to kiss this. It means a stapler.
• noruma ノルマ – A quota (business term, I think).
• panku パンク – Not a punk rocker unfortunately, but a puncture.
• furonto フロント – The front of a hotel. A.k.a reception desk.
• meiku メイク – Koichi’s personal favorite. Makeup.
• renji レンジ – microwave.
• rentogen レントゲン – An x-ray. 

The Katakana expressions above are words from foreign countries. But I cannot recognize which word comes from which country. For instance, renji レンジ is not English. 

• pechakucha ペチャクチャ – A rabble of chattering grannies.
• pikapika ピカピカ – Shiny and sparkly. Most likely where the yellow poke-rat got his name.
• panpan パンパン – A bloated full stomach. Go figure.
• kogukogu コグコグ – To drink in gulps and gulps.
• nikoniko ニコニコ – *Grin*
• perapera ペラペラ – (Italian Voice) I’m-a so pera-pera. Means fluent!
• wahuwahu フワフワ – Floaty-light or airy. Also used to describe sickness when you feel faint or drunk.
• punpun プンプン – Ever seen those cute Japanese girls that fail trying to look angry by puffing their cheeks out? Yup, that’s pun-pun. Anger.
• butsubutsu ブツブツ – Mumble-mumble-mumble. Sources say Koichi does this a lot.
• dondon ドンドン – Rapidly. We’ve gotta get going! Up the pace!
• gerogero ゲロゲロ – Ribbit-ribbit. I love frogs. Anyone know if there are any frogs that are bioluminescent?
• pakupaku パクパク – Chomp-chomp. Munch-much. 

These are some very funny onomatopoeia words. I learned that Pikachu's name comes from pikapika ピカピカ. How interesting!

Source: https://www.tofugu.com/japanese/strange-katakana-words/