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.
The Zoo and the Aquarium is on the things that never changed during the years. Everytime I visit it looks exactly the way when I first went when I was a little child. This place gives me a lot of inspiration, I like the way they want to make the cage enviroment look natural with artificiel light.
Flughafen Tempelhof was once the symbol of nazi-pride when Hitler notoriously comissioned construction of the smallest duty free shop in the world (and a beautiful example of fascist architecture). After the war, Tempelhof became one of the frontiers of the cold war with the U.S. battling the communists (who undoubtedly wanted to get rid of the small duty free shop altogether) via the Berlin Airlift. It turned out to be a huge succes, and enabled the allied forces to remain their presence in Berlin and save the small duty free shop. The real free-market victory will come in about two years though, when project developers will take over and start building houses, blocking my view onto the airfield.
Just an amazing cup of cappuccino. Try the Franzbrötchen with it for a basic breakfast. It's a place for someone who appreciates good coffee done with extreme care.