Its a huge subject you've raised here John.
One mans meat is another mans poison !!!

I will restrict my answer to only Heuer dials.

Favourite(s)
I am also a fan of the metallic finished dials. They glimmer and dance in the sunlight and you end up feeling like you got "2 for the price of 1", as the look changes.
Rich has already highlighted the dramatic appearance of the transitional Monaco and i am quick to second that it is one of the most beautiful in the range. I agree that this is my favourite Heuer dial.
Second favourite is going to be the Fume Silverstone. This is another of the metallic finished dials that gives dramatic results as you change the angle of the watch.

Worth a mention :
Favourite non-metallic dial - Montreal 110.503B (the one with the white registers)
Favourite Black and White - 2446 1st execution - Love those 3 big registers
Favourite non-chrono - 844 diver with the red 13-24 numerals on the dial

Least favourites -
Well noone likes a negative reveiw so i will start by explaining the reason for choosing this one.
I dont like chrono's with registers at 12 & 6 OR 12, 9 & 6. Clearly this highlights all Heuer's that run the Valjoux 7750 or Lemania movements. Its a matter of personal taste but i cant get past it.
My least favourite (Tag) Heuer is the first of Tag's 1887 Carrera's. They made such a hype of the "new" movement & were then crucified in the press and on the many forums for not being their own design movement but the worst for me was they chose to place the registers at 12 & 6 on the dial.

Remember - everyone has different tastes so i hope i did not upset any collectors by highlighting what i dont like.

Cheers - Darren