Frank Marshall, the U.S. Champion from 1909 to 1936, had some important ideas in the openings. The gambits named for him in the Ruy Lopez (1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 0-0 8.c3 d5!?) and Semi-Slav (1.d4 d5 2.c4 e6 3.Nc3 c6 4.e4 dxe4 5.Nxe4 Bb4+ 6.Bd2 Qxd4 7.Bxb4 Qxe4+) remain theoretically critical even today. The defense to the Queen's Gambit named for him (1.d4 d5 2.c4 Nf6) has been less successful. It is never seen today in high-level play, though it remains a mainstay among lower-rated players.
The following game shows a nice trap that is often seen. After 3.cxd5! Nxd5, Marshall's idea was that the natural 4.e4?! Nf6 5.Nc3 e5! gives Black a reasonable game, since after 6.dxe5 Qxd1+, Black regains the pawn with 7.Nxd1 Nxe4 or 7.Kxd1 Ng4. Instead, 4.Nf3! prepares e4; on 4...Bf5, 5.Qb3 is awkward to meet. 4...Nc6, as in the game below, is inferior, but popular on the Internet. White's 5.e4 Nf6 6.Nc3 Bg4 7.d5! set a trap, which Black fell into with 7...Ne5?, allowing 8.Nxe5!, a pseudo-queen sacrifice that wins material by force. After 9.Bb5+, Black's best was the abject 9...Nd7 10.Bxd7+ Qxd7 11.Nxd7, leaving White a piece up in the endgame. Black's 9...c6? was even worse. After 11.cxb7+, Black resigned in the face of 11...Kd8 12.Nxf7# or 11...Nd7 12.bxa8(R)+ Qd8 13.Bxd7#.