I am trying to do the following

E.g.

Alligator 1
Bear 1
Cheetah 1
Deer 1

Imagine the above is two column with a column of names (Col A) and the other
of values (Col B). I managed to put in a function in another cell whereby it
will look up Col B to look for value "1". If the value is "1" the cell will
display the corresponding name, i.e. Deer. However, the problem is when I
put in another cell looking for another name whose corresponding value is 1,
it returns Deer. How do I avoid this problem so that it will return me a
value that has not shown yet?