There where two (three?). I can't decide which one would be the most iconic Klingon ship. The D7/K't'inga was the first, the most majestic BUT it's not the most distinctive. As you can see there are two similar models and there's a third one - Vor'cha.

That's why ultimately I would say that Bird of Prey is THE most characteristic Klingon ship. What is more - It looks really menacing. As if it really was a living Bird of Prey