Troll Tax is a simple way to turn trolling on twitter into donations for charity. Just paste in the URL of a twitter troll's tweet and donate.
Once a donation is completed, you can reply to the troll to notify them of the donation.
Whenever you spot a troll enter their tweet's URL into the site, select a charity to donate to and then you can reply to them linking to their donation page. There's even a Chrome extension. Retaliate with kindness.