Not marketing-function specific (i.e. Spyfu for SEM, Ads Library for Facebook, etc.) but more generally -- competitors' traffic numbers, sources, bounce rates, A/B tests, conversion rates, etc.?
There are a few established players in the category: Similarweb, Alexa, and Hitwise (with varying degrees of accuracy based on the data panels they've each assembled). Any others that you've come across?
Ahrefs is a swiss army knife of content and search focused tools that's perhaps best known for its Site Audit (that shows your site's backlinks, search keyword rankings, referrers, and more) and Keyword explorer (to research related search terms, traffic, and more). But you can use the same tools behind its Site audit to explore competitors, partners, and any other site you want in its Site explorer.
Enter the domain of the site you're intersted in, and you can see a breakdown of its Ahrefs rank, backlinks, organic keywords, organic traffic, number of crawled pages, and much more. Dig deeper and you can see specific keywords they rank for and at what level, the specific pages they get the most traffic from and their estimated value, and snapshots of their paid Google ads and keywords, and estimated traffic from them. There's a competing pages list that shows content on their site that competes with your site's content, and a content gap list to suggest areas they've overlooked which you could target. It's a ton of data in one spot that on the high level lets you see their general performance, and on the low level can help you gain ideas from what worked for them.
AppAnnie is well known for mobile but to get beyond download data and into actual usage panels you can use Verto and Apptopia.
I've looked at crayon.co and it seems to provide info on what competitors are publishing that gives insight into their positioning. There is a free tier.
Not marketing-function specific (i.e. Spyfu for SEM, Ads Library for Facebook, etc.) but more generally -- competitors' traffic numbers, sources, bounce rates, A/B tests, conversion rates, etc.? ...
Wanted to start a thread of products that are SO differentiated, useful, and loved, that you'd be happy to keep paying at a much higher price point.
Especially for personal to-dos and tasks that you need to accomplish outside of your team, what is your favorite app and tricks for getting the most out of it?