Sharpie brand permanent markers are great, but I have to add that they will probably not last as long in the wash as a laundry marker or fabric marker. DH has an autographed baseball cap that the signature is barely visible after a few washings. DD has a t-shirt from a birthday party, I don't know for sure what pen they provided. It has held up very well over the years. (it's been 5 and the shirt was an adult size)