One of myt vaourites s the Romanian one - here are the first two verses - and if you click on this you get the rest, and the link to the stirring tune. It has the effect in any international match of putting them psychologically on top, I reckon (they still tend to lose in the end, but with style):

Wake up, Romanian, from your deadly slumber,
In which barbaric tyrants kept you so long by force!
Now or never is the time for you to have a new fate,
Which should command respect of even your cruel enemies.

Now or never is the time for us to prove to the entire world
That in these arms a Roman blood still flows,
And that in our hearts we proudly keep a name
Triumphant in all battles, the name of Trajan.