...and here is mine for what it is worth.
It is absolutely, positively RUDE to be talking on your cell phone when you are checking out at a store. It bugs me to no end to see people chatting away barely recognizing anyone as they throw a credit card or cash at the person across the register.
For goodness sake people. Put your blasted cell phone down for two minutes and take a second to recognize that there is a human being standing right in front of you attempting to serve you. I am sure your friend on the other end can wait two minutes to hear your mindless drivel.