Recs.
Updated
Discord is a free voice and text communication platform targeted primarily at the gaming market. It aims to match the ease of use of existing chat clients like Skype and mix it with the power of servers with multiple rooms and role permissions offered by voice clients like Teamspeak.
SpecsUpdate
Pros
Pro Friendly payment policy
Free account have no tangible restrictions.
Premium account is just a way to say "thank you" to developers. And it work for all servers of discord (not as in slack). And it can be purchased by one who wants. In contrast to Slask, where all active members of the server should be "premium".
Pro Does not allow NSFW related things to be posted unless in a NSFW channel
Cons
Con Developer's previous company was sued for privacy violations, among other things
See:
http://classactionlawsuitsinthenews.com/class-action-lawsuit-complaints/openfeint-green-international-privacy-class-action-lawsuit-complaint/
https://www.ftc.gov/enforcement/cases-proceedings/closing-letters/openfeint-inc
Discord's privacy policy also states that while they might not sell your data, a company they get sold to will quite possibly attain said data and thus may be in "more" shady hands.