Indian Defence, 1.d4 Nf6
Most popular response for Black, creating sharper games than 1. ...d5.
Closed Game, 1.d4 d5
2.c4, Queen's Gambit
Modern Defence, 1.d4 g6 (Transposing into King's Indian Defence with 2.c4 Nf6)
Transposition to Benoni Defence, 1.d4 c5
Dutch Defence, 1.d4 f5
Not frequently used by Black. It weakens the delicate f7 square and the pawn's development is somewhat awkward. The option 2.Bg5 lays an interesting trap.
Polish Defence, 1.d4 b5
Considered dubious for Black. It must be met with careful play though or Black may have a good flank attack.