I really can't think of a favourite complete stage. Bits of Hafren or Dyfi, I guess. Has to be central Wales. Some interesting choices above.
Grizedale - Another least favourite. 2 front punctures 8 and 11 miles into the 20 miler that was the first forest stage of the RAC that year. Changed them both and team mate who had one and tried to drive out on it went off and lost far more time than us. Punctured there again on another RAC. It was kinda known for them. Kullang lost the RAC with 3 punctures on it the year Toivonen first won.
Ouninpohja - Done it as co-driver. Most 1000 Lakes stages too fast and down to who practiced most and (illegally) practiced fastest.
Dikkebus - Can't recall anything special about it. Often first stage on Ypres. One fast staggered Xroads. Kemelberg only Ypres stage I recall as being rather different.
Wythop and Whinlatter - very nice one RAC when they were the only two stages with snow (caught the car ahead, hardly a regular achievement for me at that level...)
One new thought - Col d'Allos. Only ever drove it on holiday in road car but impressed by impossibly blind brow and not being able to see over the bonnet of a std RS2. (Goodness knows what it was like in a Big Healey). On the descent, the weight of wine bottles in the boot caused a moment at what Simo Lampinen called the "white shed". Even Romain Bardet (the best descender on a bike) had a serious wobble there on the Tour (or the Dauphine) a few years ago.