Another version from Glenn's :

On D2:

=IFERROR(INDEX($A$1:$A$100,MODE(IF(($A$1:$A$100<>"")*1*ISNA(MATCH($A$1:$A$100, D$1:D1,0)),MATCH($A$1:$A$100,$A$1:$A$100,0)*{1\1}))), "")

array formula entered and copied down as necessary


cheers