This is the flip-action ninja jumparoony I don't know what he's officially called Raphael:
Cool and Collected, and when he arrived he was clutching that weapon. I don't think he originally came with that weapon but who cares.
As you can sort of see, he has a little counter-weight on his back to aid in his flipping ability, sculpted to look like a backpack of sorts. It's not too obtrusive, and at least they designed it to look like something of relevance, so it does little to detract from the toy's aesthetics.
Sometimes he does land on his feet, but getting the flip action/release just right can be tricky.
But who cares, he's a cool looking Raphael and you can't have too many of those.