This thread sure has lasted a long time! I guess I'll finally post my own favorites...
My favorite real rocket with out a doubt is the Saturn V, it's the biggest, most powerfull and the only one that has taken humans to another world. All others so far really pale in comparison.
My favorite model rocket isn't any one single rocket, it's a class of rockets. I really love scale sounding rockets. They come in a plethora of shapes and sizes and not surprisingly most will fly well or really well. I lean towards the IQSY Tomahawk and several of the Black Brants as favored subjects within that class. They also tend to be easier to model if I'm scratch building.