For the most part, most new weapons didn't feel right to me, so I kept using the ones I was more comfortable with (and had powered up). At that point, the game became little more than a series of shooting galleries. Just keep following the path and shooting/stabbing everything. The gameplay never really evolved, there weren't any decent puzzles, and I just wasn't invested in the story enough to keep wanting to play. For all the acclaim the game got, I was awfully disappointed in it.
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Xbox Live: Mach Tornado
PSN: HeyGuysItsGhoul