We used to fuck around with businesses with fax machine. We'd photocopy our middle fingers like 3-4 times, tape them to each other, end to end except the top end of the first sheet and the bottom end of the last sheet. We'd feed the top into the fax and when it cameout the other end, we'd then tape the top end of the first sheet to the bottom end of the last sheet...so you'd have a continuous "fuck you" loop. People would come into work the next day, out of fax paper, and just the long roll of "fuck you" on the floor. Fun times.