Use the following formula to obtain the query you want.
Formula
=FILTER(A:A;(A:A="Combat Medic")+(A:A="Universal"))
Explained
In the reference it is explained by Ahab that +
and *
can be used as boolean expressions, as OR
and AND
.
The solution with the IFERROR
(see revision history) is of no use in this case, unless you want to find a particular string:
=FILTER(Sheet2!A:F;IFERROR(FIND("Combat";A:A);0) + IFERROR(FIND("Uni";A:A);0))
Here the IFERROR
returns 0
when nothing is found, causing the formula to still function.
Screenshot

Example
I've modified the example file to contain both solutions: Filter with Boolean
Reference
Google Product Forum, Boolean Expressions