Cloudjumper from How to Train Your Dragon 2... That dragon is just gorgeous. The Night Fury ain't bad either, but Cloudjumper easily takes the win with those quad wings.
As for the game, I think that the Kaltzentan does it for me because of the color pattern.
I'm not that into intelligent dragons; Smaug, Shruikan, and the like seem to me kind of weird although I can't explain why.
The Ryuu Ga Waga Teki Wo Kurau & Ryujin No Ken Wo Kurae Dragons are my favorite Dragons at the moment. 
Definitely smart and powerful types, and best if they can take on a human form 
like Great Western Dragons from the Shadowrun Universe or the Golden Dragons from the Witcher
as for the DAI dragons, I liked Kaltenzahn best, mostly because of the look.
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