Nouns:
* Kilo: Kilogram (weight unit)
* Koala: Koala
* Kiosque: Kiosk
* Karma: Karma
* Kangourou: Kangaroo
Verbs:
* Kiffer: To like, to enjoy (informal)
Other:
* K: The letter K
* Km: Kilometer
Note: French doesn't use "k" as frequently as English, so you won't find as many words starting with it.