so, assuming your list begins in A2 and goes down from there, I've had luck with this formula which will create a distinct list and omit blanks...
=IFERROR(INDEX($A$2:$A$15,MATCH(0,INDEX(COUNTIF(B$1:B1,$A$2:$A$15&""),),0))&"","")
the section COUNTIF(B$1:B1 needs to begin one row above the data