International Student Card
The International Student Identity Card (ISIC) is the only worldwide (including EU and UNESCO) accepted student card. It's complete with passport photo and currently valid from the date of issue (usually September of the year in question) until December of the following year.
The Student Union cannot provide an ISIC.
Normally, immatriculated students can get an ISIC at various travel agencies, if the university itself doesn't offer such service.