And Game Hunter, that is some scarily thorough analysis of AoMr. I hope someone copies that down for prosperity.
Actually I'm kind of worried it's too long, not to mention that I really didn't talk about the basics there. Builds aside, most of the tips and tricks already assume you have a good handling on how non-shotgun weapons work in a tactical environment. Thomas's guide likely does a good job at explaining this, but I can continue to give advice if you feel what you've learned so far reading this, his guide, and my own (regarding Marksman stuff at least) is inadequate.
This isn't necessarily the place to begin talking about OTHER stuff, either, but I wouldn't mind doing similar write-ups for problematic special levels, builds, or challenges. Anything but City of Skulls, because I haven't actually seen the new City of Skulls (although it can't be THAT bad if you've prepared yourself the same way you used to).