George’s Outstanding IOU
 According to an article on Contactmusic, George Harrison was $34 short when he bought a black Gretsch Duo Jet electric guitar from merchant seaman Ivan Hayward back in in 1961. So, he wrote Hayward an IOU for the amount, and promised to pay him back.
However, it seems that George never honoured his promise, and to this day Hayward still holds onto the IOU note signed by Harrison.