Of course, my favorite dragon of all time is my own!
No false modesty here.
In January of 1980, I started running Dungeon and Dragons games, after our DM went back to the states (I was in the Army, in Germany). I enjoyed it immensely. Like most beginners, I mostly used pre-written scenarios, until I became dissatisfied and started writing my own. My biggest beef was the way dragons were treated. They were always presented in little tiny cubbyholes, unable to easily turn around, let alone use their full abilities!
Then came a convention in Orlando, Florida. My first experience in
Judge's Guild's
Liche Lords scenario! We were actually attacked out in the open by a powerful dragon! I loved it! We successfully drove him off, and continued on. Just before the final encounter, we happened on the caves we figured the dragon resided in. Much smarter for us to take on the behemoth there, rather than in the open again! Sure enough, there he was - in a tiny cubbyhole he could barely turn around in.
I fumed.
And I went home and created Darganau. A "by-the-book" red dragon, who took full advantage of his intelligence, and the availability of those things that would help him.
And his cave is no cubbyhole!
I've ran him - in one way or another - with every group I've had. Most have been smart enough not to take him on - though some were not convinced until entering the final lair in his mountain home! He
has been defeated once, by a group at
GEN CON no less, due to a failed take-off! (he
is a huge creature!)