Hi Chetan,
I assume your data is from A2 to A11 (A1 is your header) as follows:
Header1
A
B
A
S
D
A
R
A
R
M
Now, at B2, write the following:
=IFERROR(INDEX($A$2:$A$11, MATCH(0, COUNTIF(B1:$B$1, $A$2:$A$11)+IF(COUNTIF($A$2:$A$11,$A$2:$A$11)>1, 0, 1), 0)),"") CTRL + SHIFT + ENTER (to enter it as an array formula) and drag it down as needed.
Note: Change the reference per your need.
Regards,
Kaushik