Kettlebell Rotational Swing
Take your standard kettlebell swing and, as you can guess by the name, add a rotation into the mix. Outside of the obvious twisting nature of the movement, the only real difference is going to be foot position. Since you are rotating to the side each time you bring the kettlebell down, your feet are going to be closer together, almost touching. You will have two rotating movements here. At the hips, just as with a regular front swing, and one around the obliques, which will allow for the side to side motion.
Notice the foot position here. My feet are much closer together, which, as mentioned, will allow for the rotation around the abs. This will get the obliques more involved in the movement, along with the hips and glutes as with a normal kettlebell swing.
I threw the side view in just to show you that, as with the regular swing, your main focus(es) should still be the same. Chin and chest up, eyes forward. This will help keep your back flat and not rounded over. Also, the main driving force should be your hips, not your legs. Use your hip and glute muscles to swing that kettlebell back up once you bring it down. Remember, though, especially with the twist added in, if your low back begins to tighten, use your legs a little to relieve some of the tension.