Discord too. A lot of people elsewhere in this thread are talking about how Slack is eating a ton of RAM and things like that, but (anecdotally, of course) Discord seems to be a lot better while using a lot less RAM. Personally, I can be in ~80 Discord "servers" that total to a few hundred thousand people and it's still using <500MB of RAM, so clearly it's possible to do a good job of resource management.
