That's really funny. As soon as I saw this thread, I going to put up the Madness Combat series as well. Whatever, good to know that somebody else watches it. (Go to http://krinkels.net/ if you want to see more, by the way.)
Anyway, the Castle series is one that I have always enjoyed. Check it out: http://www.newgrounds.com/collection/castle.html
By the way, the first castle (not the prologue) is not very good. The second one is OK, but the third one (Broken up into several parts) and the repercussions series are extremely well done, and really push the flash format to the limit. Because of this, my advice is to stick through to the end.