A place where I spend some time almost everyday is the Marheineke Markthalle on Bergmannstraße in Kreuzberg. It's just around the corner from where I live and a great place to buy fresh food and products from local farmers or all kinds of delicatessen from different countries. Many market stalls also sell freshly prepared food and it's always busy at lunchtime. For saturday mornings try the original french croissants.
Chalet is one of many clubs in Berlin. It's a very interesting option if you want to know what Berlins night can be. Music is great and environment too. It 's a decadent building in the inside with curious corners...
My favorite lake to visit during the warmest months. It's located in the southwestern part of Berlin and it's reacheable by public transportation, just around 40min from the city center.