AirHelp assist air passengers around the world secure compensation for delayed, canceled, or overbooked flights.
Mixpanel has a good UI.
It has all the same bells and whistles and is much cheaper than Salesforce.
Skype is universal. Everyone knows it. It's easy to connect, share files, chat, talk and share your screen. (used for external communication)
We use Payoneer for outgoing payments. It's okay, but most payout providers are UX restricted by the banks KYC requirements.
It's very simple and easy to learn. It's not as comprehensive as JIRA, which is what we would use if we could afford it.