"František!"

Translation: Františku!

[LauPaSat]

Is vocative often used in Chech, or like in Polish only in formal situations. I mean if your friend's name is Frantisek would you call him Frantisek or Frantisku?

[VladaFu]

It is always used.

[sebytro]

How awesome, I knew this one from the movie Smrádi.