Bagon, Shelgon and Salamence - never used
Dratini, Dragonair and Dragonite - remember having them in Pokemon Red. Great creatures
Trapinch(I know it is not a Dragon Pokemon), Vibrava and Flygon - never used
Horsea, Seadra and Kingdra - not used, but I know Seadra and Kingdra are a pain to use
Swablu and Altaria - do not particularly like their style
Latias, Latios and Rayquaza - not used/caught
All in all, I vote for the Horsea/Seadra/Kingdra option. They're pretty tough, screw Horsea, that's weak hahah, but the others are awesome.
Dratini/Dragonair/Dragonite come in a close second for classic awesomeness.