According to the Chess.com Master Game Database, of the following (4) common openings for white, 3 of the 4 have the same most common response for black. Without looking at your openings database, which of black's first move is the most common in (3) out of the (4) openings for white.
#1. e4
#2. d4
#3. c4
#4. Nf3
PS. Apologies to Mike for bringing openings into the discussion.