Hey, do guys know of any openings for black that are more or less "forced" in some way?

When I say "forced" I mean like the Ruy Lopez as White -- after E4 e5 nf3, nc6 is basically the best move and is then "forced"...

The sicilian is strong, and I know my share of the theory behind the Najdorf but I dunno why all my opponents just try to four-mate me whenever I do it.. it's sad.

By this definition, all mainline openings are 'forced'.