The Jerome Gambit is full of "reasonable" lines of play for Black, and the defender has to be aware - is it a playable reasonable line, or an unplayable reasonable line; and then, more importantly, what comes next?
Wall, Bill - TenAndOnly10
1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+
4...Kxf7 5.Nxe5+ Nxe5 6.d4 Bb6
This seems like a reasonable move, although not frequently played in comparison with other lines. It shows up in 111 games in The Database, where Black scores 50%. (Compare that to the 1,528 games with the same moves up until 6.d4, where Black scores 48%.)
Of course, any chance of catching Bill by suprise is likely to be small.
7...Qh4 8.Qf3+ Ke8 9.Nc3 Ne7 (9...Bxf2+ 10.Qxf2 Qxf2+ 11.Kxf2 Nh6 12.Nd5 Ng4+ 13.Kg3 Kd8 14.Bg5+ Nf6 15.exf6 h6 16.fxg7+ Ke8 17.gxh8=Q+ Kf7 18.Rhf1+ Kg6 19.Qxh6 checkmate, Wall,B - Shillam, lichess.org, 2016) 10.g3 Qh3 11.Be3 d6 12.Bxb6 cxb6 13.exd6 Ng6 14.Nd5 Qd7 15.Nc7+ Kd8 16.Nxa8 Qxd6 17.Rd1 Ne5 18.Rxd6+ Ke7 19.Qc3 Kxd6 20.Qd4+ Ke6 21.Nc7+ Kf7 22.Qxe5 Rd8 23.Nb5 Bg4 24.Qf4+ Kg8 25.Qxg4 a6 26.Qe6+ Kh8 27.Nd6 Rb8 28.Nf7+ Kg8 29.Nh6+ Kh8 30.Qg8+ Rxg8 31.Nf7 checkmate, Wall,B - Itboss, lichess.org, 2016;
7...Qe7 8.Qf3+ Ke8 9.Nc3 Qxe5 10.O-O Nf6 11.Bf4 Qh5 12.Qg3 d6 13.Qxg7 Rf8 14.Nd5 Qf7 15.Bh6 Nxd5 16.Qxf8+ Qxf8 17.Bxf8 Kxf8 18.exd5 Bf5 19.c3 Re8 20.Rfe1 Be4 21.Rad1 Kf7 22.Kf1 Re5 23.f3 Bg6 24.Rxe5 dxe5 25.Ke2 e4 26.b4 exf3+ 27.Kxf3 Bh5+ 28.g4 Bg6 29.c4 a6 30.d6 cxd6 31.Rxd6 Bb1 32.Rxb6 Bxa2 33.Rxb7+ Ke6 34.Rb6+ Kd7 35.c5 Black resigned, Wall,B - NN, lichess.org, 2016.
8.O-O Be6 9.Qf3+ Ke8 10.Nc3 a6 11.Be3 dxe5
For now White has only one pawn for his sacrificed piece, but Black's uneasy King comes close to making up the rest of the compensation.
12.Qh5+ Bf7 13.Qxe5+ Qe7 14.Qxg7 Qf6
15.Bh6 Bd4 16.e5 Qg6
This move allows White's pieces to become troublesome - enough so that Stockfish 8 suggests instead that Black give back the exchange with 16...Qxh6 17.Qxh8 Rd8 and then exchange some more pieces, e.g. 18.Ne4 Qg6 19.c3 Qxe4 20.cxd4 Bd5 21.Qg7 Ne7 22.Rfe1 Qg6 23.Qxg6+ hxg6 where White only has an edge.
17.Qf8+ Kd7 18. Qxa8 Qxh6
Black returns the exchange in his own way. The difference is that he is not now as equipped to protect his King.
19.Rfd1 c5 20.Qxb7+ Ke8 21.Qb8+ Ke7 22.Ne2 Bh5
A final slip.
24.Nf5+ Black resigned