Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...d5/5. exd5/5...Nxd5/6. Nxf7/6...Kxf7/7. Qf3

=Fried Liver Attack=

7. Qf3+
White gives check and attacks the Knight. Black's king has several moves, but only one of them is good. The worst is        7...Kg8?? which loses to 8. Bxd5+ Qxd5 9. Qxd5+ Be6 10. Qxe6# (or 8. Qxd5+ Qxd5 9. Bxd5+ Be6 10. Bxe6#). 7...Ke8? doesn't work because of 8. Bxd5. Black has to defend the knight with Ke6.

Theory table
.
 * 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Nxd5 6. Nxf7 Kxf7 7. Qf3+