The physical performance aspect of goalkeeping is largely about lower body reactive movement. To that end, here's another of my favorites, the kettlebell swing. Watch the video first:
What I like about this exercise is the way it combines building explosive, reactive strength with a cardio element. Traditional squats are a great strength and mass building exercise, and as a lifetime member of the Skinny Legs Club, I include them in my training. But I feel the kettlebell swing is more directly related to athletic performance.
There's one more exercise to come in this series, and if I'm brave, I might just video myself doing it. We shall see.