Great question which I think is still very much relevant in 2017. There are lots of SEO tools available for keyword-analysis, ranking, content-ideas, link-building, competitor-analysis e.t.c available in the market today, however, my brother uses Xovi and Seolytics quite regularly; to which i coincidentally found included in this list as well https://www.1and1.co...ls-at-a-glance/
He reckons, compared to the job that these two do, the prices of these two tools are very affordable. That being said, i tend to think that there are lots of different approaches to making your perfect SEO tool. Good luck!