In reply to Offwidth:
I would imagine the best would be the Cuillin traverse - though I've not done this yet. In fact, I've done no rock climbing in Scotland, and it seems a shame as routes like Punster's Crack, the Cioch Nose followed by Integrity, and Sou'Wester Slabs look thoroughly fantastic. The latter is just beautiful to look at - a huge, granite-plated armadillo!
I would imagine that the worst would be Great Gully, followed closely by Clachaig Gully and The Chasm! Or the same routes in a different order!
Post edited at 14:27