I know what you mean Geoff.. I've struggled with that one too - I remember one occasion when DS was climbing trees in the park with a couple of little girls from his class, and one said to me (very proudly) "I don't like girl stuff, only boy stuff" (which was pretty much me at that age).
In that respect I think it's easier parenting a boy - I could give him the "girl" stuff (my old dolls' house, a toy kitchen) without worrying about him internalising a message about "and this is the only stuff you should play with" (which is a worry with girls).
I stuck to a "no girls/boys toys, just stuff you like/aren't interested in" line (with a side order of "some toys are intrinsically better toys - I know this is bright and shiny and advertised on TV, but how long will you be able to play with this before you get bored?"
For me the traditional toys coded "girl" which are worthwhile are the ones that open up a child's imagination (dolls houses) or open the way to creativity (toy kitchens and an interest in cokery, sewing kits and a whole range of craft products). The crap ones are typically the ones that push messages about personal attractiveness being the be all and end all.
(Ditto "boys" toys - the good ones encourage creativity, construction and engineering skills, outdoors adventurousness, which should be encouraged in both sexes, the crap ones are the mindless destruction ones).