In reply to Tim Chappell:
25, 33 and 40 are probably my favourites. It's a mixture of the areas covered and the quality of the cartography, which seems to vary from area to area, but is only particularly obvious where there's lots of rock.
25 has Torridon, Strathcarron and the Mullardoch/Monar wilderness on it.
33 has Knoydart, Glen Elg and Glen Shiel - got to love the area around Arnisdale and Loch Hourn
40 is Ardgour, Loch Shiel, Loch Morar and all those fun places.
There are areas further north that I rate just as highly, but for some reason the maps don't inspire me as much as the ones above. 26 is also of interest for local stuff.