There's plenty of good ones, depends what style you like. As for my favorites, New England has the 1-5-5 prowl, Multiple D and NYJ are very versatile, and Tennessee has the 4-4. Pretty much decide if you want to use 3-4, 4-3, 4-6, or a combination of them. Most playbooks are pretty similar, I'd say playbooks are much more important on offense than defense. Just pick something, work with it a lot, and you'll be fine.