Can you go completely open source??

I have been using open Source software(OSS) for quiet long time now, OSS offers wide variety of software for every reqiurement, from making a presentation to Vector 3D Graphics,imaging,animation,programming CAD/CAM,manging Servers.....etc you name it & OSS has it.So here's a challenge, enlist me the name of any proprietary software & i will suggest you an OSS equivalent to it(infact a much better one!)...