If you've purchased Starkist tuna in the last 5-6 years or so, there's a class action lawsuit because they underfilled some of the cans, and it looks like you have the option to receive either $25 cash or $50 in tuna certificates. You do have to register on the website, but no proof is required - honor system only. Must file by Nov 20, 2015.

https://www.tunalawsuit.com/home.aspx