Yksi: ...used by the White Guard to separate Russians from Finns in the Finnish Civil War during the invasion of Tampere..... and I didn't think it was all that hard to pronounce...
Höyryjyrä: "Steam Roller" ...Finnish soldiers in World War II used this as a password, as only a native Finnish speaker could properly say this word.... Hmmmm..."Hey, I'm Finnish...OK, pronounce this word.... höyryjyrä"....
And here are some Finnish sentences that can be turned into to jokes:
Olin seitsemän vuotta sedälläni kodossa renkinä ....apparently this can be used to tease people from Tavastia...
Kurri etsi jarrua murkkukasasta. ...this one can be used in a rather nasty and/or cruel way....
So any native speakers want to give these a go?? ...and maybe add some more??....

