In this city, spectacles such as Opera or going to a classical music concert are much cheaper than western Europe, and the quality is surprisingly good, so you won't feel like going to the cheap version of Viena Orchesta but a really good one. Also, Slovaks are mad about Ice Hockey, and Bratislava has a very modern stadium called Slovan Arena.
If you want to go to the stadium, you can purchase your tickets in the stadium (reachable by tram 9) and bookstores in the centre, as well as throught their fully english website. Prices range from 14 to 20€ and all ISIC card holders have a 10% discount on each ticket! Season starts on September and finishes on February, so pay attention not to miss it!
Bratislava Shooting Club offers you a wide variety of activities! From shooting real bullets with real weapons (including AK47) to a safer way to shoot your friends: PaintBall and Airsoft! They have several facilities, one in the outskirts of the city and another about 15 min by car (they offer pickup). It's a nice option for an action-packed day! More information here.
More sections such as: Opera, Theatre, Philarmonica, and Horse races will be added soon!
This is the definitive guide for a Erasmus or a Student in Bratislava, all info I know about the city will appear here