Berries is used for flavouring meat and fish as Andy_e mentioned (the blue berries are used not the green ones) and as flavouring in gin and genever.
The berries could be crushed and boiled, preferably with sugar added, to a pulp wich stiffens while cold. This is called "treak" and was used both as candy and medicin (I`ve never tried this myself).
The berries have also been crushed and used with oil or tar as a remedy against scabies.
The needles/berries was boiled in water and used as hairwash or washing containers used when brewing beer, washing the floors and so on.
And a juniper branch over your door will ward off evil spirits
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Tor Helge