We are slowly migrating everything to Zoho CRM, from our previous system with Excel sheets. The price is good. The REST API integrates with our source of data and has many services, for example for customer support and email marketing.
We also have a Slack channel. I’m not such a big fan--managing the log-ins when you are participating in many different channels is a bit clunky.
Our Dev team uses Discord. It is a bit of an odd choice because it’s a chat used for gaming.
We rely a lot on Skype even though it often has some problems with the connection.
We use Zendesk, which has a very nifty chat tool. I like the fact that I can see how active our site is at any moment. The only downside is that they don’t have a visitor history--you can only see past discussions, not past visitors.
I like Dropbox. The fact that it is overriding files when two people are writing at the same time or if one has forgotten to close it is a little annoying. The collaboration aspect is not as good as with Google Docs.
Soply is a great marketplace to find unique designs for your website and marketing needs. It brings together design freelancers from all fields (photography, film, animation etc.) and a great system for matching you with relevant artists. You can get something custom-made at a reasonable price.
We have no problems with Stripe--it was very easy to integrate. Something I would wish for is even more flexibility for how to handle your different pricing plans and transition between them.