Great question. The ship I find most iconic for Klingons is the D-7. It has a certain majesty and danger about it. Especially with that fly-over shot in the motion picture (and the music!).
However, the ship I identify most with the Klingons would certainly be the Bird of Prey. I also have a special place in my heart for the Vor'Cha, since it was my first Klingon Star Trek Toy which was gifted to me after a serious accident. It seriously made me feel better.