Vaksn zolstu vi a tsibele mitn kop in der erd!
May you grow like an onion with your head in the ground. or-
Zoln dayne beyner zikh brekhn azoy oft vi di Aseres-Hadibres.
May your bones be broken as often as the Ten Commandments.
and just for yucks...
Loyfn zolstu in beys-hakise yede dray minut oder yede dray khadoshim.
May you run to the toilet every three minutes or every three months.
Megulgl zol er vern in a henglaykhter: bay tog zol er hengen un bay nakht zol er brenen.
He should turn into a chandelier, so he'll hang by day and burn by night.
Got zol af im onshikn fun di tsen makes di beste.
God should visit upon him the best of the ten plagues.
*applause*
You should be a diplomat.