There are really 2 major themes:
2. Lifters (Horizontal W, Inverted W or M)
After these 2 most prevalent themes you have some more funky things like submarine and then there's Mike Marshall's linear mechanics (have fun just trying to understand that one, let alone finding an example).
You have all sorts of variations on these 2 themes. Detailed differences abound. Today, in the majors, the lifters and their variations are by far the most common. You do have slingers or swingers but not as many.
Examples of W's are Wagner (big detailed approach difference here but a W nonetheless), Clemens, Kazmir, Brown, etc., etc. Inverted W or M's include Mark Prior, Smoltz (to a lesser extent) and many others. Freddie Garcia is probably a good example of a swinger.
Regardless of the type, they ALL go through what's close to a high cocked position at footplant. No, the ball isn't facing centrefield. That's a misunderstanding by those who recommend it. It's more like 3rd base in reality and toward SS at the most.
They also ALL go through full external rotation of the humerus (forearm laid back to horizontal just as the shoulders have squared to the target). This maximizes range of motion and makes full use out of the elastic properties of the muscles and connective tissues in and around the shoulder. Now, that one creates the paradox for pitchers. That which begets velocity also increases the risk of injury.
This is one of the "common elements" in all of the arm action types. Full external rotation is a "necessary condition" for optimizing velocity. There are others, of course, but this is one.
How you get to and through this point is what varies.