Every UPC (Universal Product Code) barcode in the world is divided into two parts by three markers (the beginning, middle and end markers). These markers have the same 'bar-space-bar' pattern (101) as the barcode number six. So every product carrying a UPC barcode also carries a mark resembling 666.
"And [the Antichrist] causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads:
And that no man might buy or sell, save [except] he that had the mark, or the name of the beast, or the number of his name.
Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six ". - Revelations 13:16-1
This barcode T-Shirt doesn't have 666 in it though. We ran out of pixels. Or does it? Mwah ha ha ha ha. No, it doesn't.