My favorite castle set of all time would be 973158 UCS Kings Landing from 2135...

(Up until NOW would have been more accurate...).

 

One of my sentimental all time favorites would be 6081 King's mountain Fortress though as it has been my first one.

Since it's rather small and insignificant compared to newer sets I would say one of my more favorite ones are from the Kingdoms series:

Market Place, Joust, Mill Village

I also like the LOTR Stuff but it's not castle is it?...

 

I still hope for something huge! At least they could make a series where they combine elements. Who does not want to have a huge castle? So up until now there have been some MOCs I've seen but nothing that has really satisfied me that far :-(

Of course I always kind of liked the Lion Knights as the represend the good guys.

 

Still my Dragon Knights have been more of a legion and I also liked them quite a lot.

 

But as for my favorite I would like to speak in favore of the falcon knights since they've always just have been a small fraction but I really liked their (early) design. I think it's time that they return with a new design! What I always liked about them was that (at least to the child version of me) they always could be the good or bad guys, though more often they've been the good guys (of course!).

 

Anyway I never was too happy about LEGO always returning with new versions of the Lions... I mean a kingdom needs more than just the lion knights! Give us some series featuring other fractions as major fractions pretty please! :-)

The yellow castle 375/6075.  Came with about 12 minifigures and cost $50.  Was this the best design? No.  Was the color really odd? Yes.  But I probably spent over 100 hours playing with it.  

 

The Market Village and Kingdoms Joust were great builds, but since I am in my 30's now, they don't evoke those special feelings like good ole Yellow Castle does. 

 

Yeah me too, I just picked it up from my basement. Many pieces are of course missing, since my sisters kids have played with it. But the box is there and the instruction. Many fond memories. It seemed so big back then like everything does in your childhood! When I get the time I'll see which pieces are missing.. 

This is for the classic fans. Funny how the set seemed a lot bigger when I was a kid. Ha.