Unfortunately, when all else fails, I find something that they hate doing as a consequence to give them. Usually, that's copying words and definitions out of the dictionary or thesaurus. It usually doesn't take many times of this, plus they might actually learn some new vocabulary.
Plan some fun activities, experiments, etc. and let them know that those who are not following the rules (talking, etc.) will not be allowed to participate. Usually I only have to do one or two activities while the talkers do some book work before they get the idea and settle down.
but I try not to penalize the few kids who aren't talking - who actually never talk. So I just keep a list of all the kids posted on wipeoff paper on the board. They talk and they get a 3 minute check. Those minutes really add up. Haven't had much of a problem with rampant talking since I put this into effect.
I wish I had a recess to take away! I require my miscreants to remain in the room when everyone else has been dismissed until the tardy bell. That takes away their roaming-in-the-hall time! My most talkative students in my last class also walk home. I make them stay until bus riders are dismissed and boy are they steamed about that!!! It's not much though, only about 4 minutes for most.