Stuff it...cut it in half lengthways, cut out the seeds, shove in whatever and put on some cheese and bake it - leftover chicken and veg in a cheese sauce, leftover bolognese
chop it up and use it to stretch a casserole or curry
make rhubarb and marrow jam and remind all the really wrinklies like my mum how lucky they are that the war is over
marrow is basically flavourless vegetable mush. a real wartime veg. i loathe it.