We switched to Nightwatch from Stat after some issues and realizing they support wide range of functionalities with have a more friendly interface. Happy so far!
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Majestic - Majestic - Link intelligence tools for SEO and Internet PR and Marketing. Site Explorer shows inbound link and site summary data.
Serpstat - Search analytics, Rank tracking, Backlink analysis and Site Audit tool.
Ahrefs - Ahrefs is a toolset for SEO and marketing. We have tools for backlink research, organic traffic research, keyword research, content marketing & more. Give Ahrefs a try!
SEO Tools Centre - SEO Tools Centre provides SEO checker services for websites.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.