If you're looking to strengthen your core muscles as well as your shoulders and arms, here's a great move called the suitcase walk [1]. Not only is it great for toning your muscles, but it can also prepare you for carrying your suitcase in the airport this holiday season. Here's how to do it:

• Hold a rather heavy size dumbbell in your right hand, between 15 and 30 pounds. You want to choose a dumbbell weight that will challenge your core, but also allow you to have good form when walking. Hold the hand weight to one side with a straight arm, just like you would hold a suitcase. Keep your shoulders even and your posture square.
• Walk, carrying your dumbbell at your side, for 100 to 300 feet. If you don't have one long area to walk in, then walk a shorter distance, back and forth, to total the amount of feet you've chosen. Keep your spine straight and your abs engaged as you move with control. Don't swing the dumbbell mindlessly, but keep it at your side.
• Then bend your knees to put the weight down and pick it up with your left hand. Walk the same distance.
• Do this exercise once or twice on each side, envisioning the long lines at the airport.

Source [2]