First one: UNITED AIRLINES (Dulles Airport) at the check in counter. It was for a direct flight to Beijing. There was a long line that day. When I got to the counter I asked the European lady if she could check to see if all my luggage will directly go to my final destination. She told me "no." When I asked if she could help me sync my flights so that I didn't have to recheck my luggage, she told me that she couldn't do it. She told me to step aside so I could call my flight agent to figure out what could be done. And I did. In the mist of me making the call, she switched shifts and a new lady came out. After I was done, I walked up to the counter (i was standing to the side about 2 feet away) to explain that the lady earlier was helping me, told me to step aside to make my call, and the result of my call. The new lady refused to help me. At first she ignored me when I said "excuse me" to her. Then she proceed to glare and scream at me "I DON'T CARE WHO YOU ARE. YOU NEED TO GET BACK IN LINE." Afterward, she completely ignored my existence and continued to service the other people. Ironically the plane I was on that day, 30 mins into its departure, the right engine blew out. The pilot had to dump fuel and re-land. I didn't even get to leave the country until the next day. I heard this incident was reported on CNN. This has got to be my WORST customer experience ever!
Second: BEST BUY (Pentagon Centre) at the check out counter. I was buying a new computer that day. When I got to the counter I asked the cashier a question about the rebates. She probably did not know the answer. She told me if i had any questions, that I should go back to the Tech area. Then she pushed my cart out of line and proceed to ring up all the items of the people standing behind me! I refused to go into that store thereafter.