From my /Application folder (the italic ones are vital to my workflow): AirServer/AirParrot, Charles, Coda, CodeBox, Day One, Kaleidoscope, Keynote, Messages/FaceTime, MindNode Pro, Mou, Numbers, OmniFocus, OmniPlan, OmniGraffle Professional, Opacity, QuickSilver, SourceTree, TextMate, Transmit, VoodooPad, Xcode (and InterfaceBuilder and Instruments)

Most of them have Windows/Linux equivalents, but for me aren't nearly as good as Mac versions (your mileage certainly varies).