=IFERROR(INDEX($C$4:$C$28,MATCH(1,INDEX((COUNTIF($C$4:$C$28,$C$4:$C$28)=LARGE(INDEX(COUNTIF($C$4:$C$28,$C$4:$C$28),),1+SUMPRODUCT(COUNTIF($C$4:$C$28,$C$29:C30))))*(COUNTIF($C$29:C30,$C$4:$C$28)=0),),0)),C30)

this returns a 0 if all values are the same, maybe i need to replace a 0 with c30, ah, now I'm becoming lazybrain, heh heh

Cheers,