Tox is a peer2peer IM protocol that allows sharing files, Audio and video calling and can be easily made to use tor, you can also create endless new accounts without having to give any information. It offers a great deal more than most of the apps I see being recommended here (wickr, signal and chat-secure).
First off: wickr is garbage. I have it and don't use it for anything that requires actual security. Mostly just bullshitting with friends.
Now that that's out of the way: Tox looks promising but it's a work in progress, to put it generously. The whole point of something like Signal, Chat Secure, or Silent Phone for me, at least, is that they provide a passable level of security and do so conveniently (through well designed mobile apps). If I'm not going to use it on a mobile device, I might as well just boot up Tails and shoot a PGP message to whomever I need to communicate with.
As far as Signal goes, the only problem I have with it is that it's secure but not anonymous - you register with your phone number. My favorite has to be Silent Phone. It's both secure and decently anonymous - I suppose you could be deanonymized by way of the payment method you use to pay for the service. Honestly though, if whoever or whatever agency is trying to find you is digging that deep, you've got bigger problems.