Franz is a simple messaging application which supports 14 popular services.
The program works with Skype, WhatsApp, Steam Chat, Facebook Messenger, Slack, Telegram, HipChat, GroupMe, ChatWork, Grape, Discord, WeChat, Hangouts and Glitter.
It's also extremely flexible. You don't have to choose a single service and log on just to that. You're able to add logon details for multiple services, including multiple accounts on the same service, then switch between them in a click or two.
Inevitably this "one size fits all" approach means you don't get all the options provided with the original chat clients.
But this is still an early release and the developer says more service-specific customisations will be arriving soon.