I can't just pic one.
My top 5, in no particular order:
1. Burg Eltz, Germany
Its so beautiful and its in such a nice loction, so fantastic, but the best part is its really medieval!
Ok, its not a real CASTLE, but its the prettiest manmade structure in the world IMO. What a great loction too, King Ludwig had great taste.
3.Warwick Catle, UK
Great Castle, it really looks like one. I love too how this castle in not symetrical. It was built over many centuries, and it looks that way.
4. Burg Stahleck, Germany
If you haven't noticed, I have a love affair with German Castles. I really love Stahleck. The cozy secure feeling of this enclosed structure really appeals to me, it is inspiration for my current castle project.
5. Conwy Castle, UK
Welsh castles are the best! This is so powerful and easily defendable. What is awsome about this is how if is build on a rock!
Well thats just a few Bodium, de Monte, Rochester, Dubovac, Tower of London, Sully, and Bunratty are all up there too. You see its too hard for me to just pick one, when I love so many.