What's your favorite new exercise you recently discovered?

Personally, I had to stop doing Barbell Squats because of form problems, and watched a video by Dan John per someone's recommendations on a different forum, and discovered Potato Sack Squats. They're done with a kettlebell, and I really am enjoying them and how they're helping me with my form and getting enough depth.

Here's a video starting from where he introduces the Potato Sack Squat.

http://www.youtube.com/watch?v=NjbPo-EX_5o&feature=youtu.be#t=12m53s