Slams are fun for power and energy system development. Common slam tools are medicine balls and heavy "battle" ropes (but not cats). Unfortunately, people often shortchange themselves by slamming using primarily their arms. This limits the muscle involvement and so the power (and calorie burn) of the exercise.
Instead, get your body weight into your slams, as shown in the video below.
(No cats were harmed during the making of this video. Not by us, anyway.)
Be seeing you.
-gary