It is widely held and accepted that Agile Principles and Methodoligies are best suited and in most cases preferred for software development projects. For the benefit of those Project Managers without

I find waterfall to be more preferable if your requirements are extremely well documented and inflexible. There's no learning curve on any of the technology that may be used/utilized/required. You have excessive resources and don't need to optimize the work flows. Finally, if you know the project is going to be short. Unfortunately, it's very rare where you have these sets of unique circumstances which is why agile is so attractive for software development projects. With that said, PMP isn't a methodology it's a certification based on the PMBOK and the PMBOK does have some agile branches in it, at least the next version will from what I'm told. So you shouldn't think of the PMP as waterfall, your PMP is project management - and project management has a lot of paths that you should look to achieve mastery in.

Agree with everything you said, Justin.
One of my Agile coaches told me there's nothing wrong with a Waterfall approach, and he actually preferred it when the product was relatively well-understood and simple. That was the first time I realized how counterproductive the "Agile vs Waterfall War" is to project management.

The first thing to understand is: you have an approach in one side (agile, lean, etc), you have a project life cycle in other side (waterfall, iterative, incremental, etc). So, you can mix the approach with the life cycle as you want. The "easy" way to mix them is by using a method or methodology based on one aproach plus a project life cycle. For example, SCRUM or DSDM just in case of agile. When you have the approach + life cycle then you can see if the convination matches some project management way/best practice/guideline as you wan to name it. For example, PMI style checking the PMBOK. Behind all of this, to make the decision about what you use, you have to understand that anything you use will impact your whole organizational architecture. You can use models like Tom Peter´s Seven S model to evaluate the impacts your decision will take to not fail.