Marshall in Ruy-Lopez C89:

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!

Marshall is not of course "clear win for black". I often (OK, not that often
anymore :) have positions, when white are +1.5 out of book, and black just loose
without getting any chances.
I noticed that DeepFritz plays much better in Marshall than Shredder
on the black side.
There are different openings you have to be prepared for, if you want
to play Marshall, or Ruy-Lopez in general:
1.e4 e5 2.f4 - king gambit
1.e4 e5 2.Nf3 2.Nc6 3.d4 - scotch
1.e4 e5 2.Nf3 2.Nc6 3.Bc4
1.e4 e5 2.Nf3 2.Nc6 3.Nc3
And some Ruy-Lopez variants:
5.Bxc6 - it is considered equal, but Blokhine with DeepJunior9 destroyed me in this opening :)
Early d3 - closed Ruy-Lopez
8.h3 and 8.a4 - antimarshall variants

Black sacrifice early a pawn in the center on e5 to get an attacking position.
I got interested in this opening after I lost as white a long game with
much weaker computer. It is not easy using standard book to play Marshall
white side, if you do it - I will win a game with you in the book :)
Why? Because engines play badly the Marshall. Engines show a big advantage
for white +2, and then suddenly it will change to -2, and black wins.
Sometimes an engine may find a good continuation for white, but it does not
happen often. Black in Marshall has easy plan: attack the white king.
It is not easy to play this opening as black either, because as soon as
black is "out of book" the engine will often start to defend, instead of
crazy attack at white king.
I don’t play Marshall as human, but with this opening I am able to beat
my PocketFritz2 playing the black side. All other openings I can only make
a draw, if I don’t make a mistake.