Here's a different format of shirt for 2017: A Tank-top Tee.
This mottled gray tee has wide straps for the shoulders, and no sleeves. Its slogan is "Know Your Enemies". It has a large square with CG Sonic's face in it right in the center, with a few colored squares scattered behind. Peeking out from behind the square you can see Eggman pointing, Shadow & Jet the Hawk. (Is Shadow really an enemy though?) Featuring some different characters than usual (especially Jet) keeps this shirt freeling fresh & different. The tank-top style also helps, since it's uncommon in both the USA and UK. This is a 'boys' item, but doesn't seem 'little kids' exclusive. Where is it sold?