As far as I know the English word that can be repeated sequentially the most number of times and still make perfect sense is that and it can be repeated six times: he said that that that that that that followed….. If you pause after the third that the sense becomes clearer.
I think that one of the nicest sounding words in English is fartleberry. It has such a soft, fruity sound and yet it refers to something quite unpleasant. Fartleberries are the pieces of excrement clinging to the anal hairs – I use the because of course it could never be your or my!
A French word of which I am fond is grincheux, -euse which can be used as an adjective to mean grumpy or grouchy and as a noun to mean a grumbler or grouser. You might think of me as un vieux grincheux or an old grouch.