Saying goodnight in another language may seem a little pretentious; it is. But trust me, the more you say it - the less you care.
My mother often said " bonne nuit ma cherie", french for good night my darling and I absolutely love it. Sometimes I'd remember to say "bonne nuit Mama" back.
Once you start saying it over and over, it just slips off your tongue instead of the usual boring goodnight, and your bid is much more the sweeter.
German: Gute Nacht, Mien Lieben (ha! The Young Victoria, anyone?)
Italian: Buona Notte