Avoid clubs that play what is known in Croatia as “Turbo-folk” music. These clubs are often featured in the local newspapers as violence erupts in them quite easily.
Avoid strip clubs at all costs. Most of them are often run by very shady characters, and often overcharge their guests. Recent cases include foreigners that were charged €2000 for a bottle of champagne. These clubs overcharge their customers to the extreme, and their bouncers will not have any mercy if you tell them you are unable to pay. You will soon find yourself in a local hospital. This not only applies to strip clubs in Zagreb, but also all over Croatia.
Steer clear of any drunk and rowdy groups of young people you might encounter in the street (especially on weekends at night) or night trams as random beatings have been known to occur. It is not uncommon for such groups to start unprovoked attacks on passersby, although they target mainly younger crowd and teenagers. These are not common but they do happen occasionally, so take precautions.