Take a look at the volkls the v pro or the v explosive depending on how fat you want, volkls in general tend to be stiffer than a lot of the other makes...
umm, the mothership is about the softest fat you can find. the volkl's are pretty stiff, so are the new atomic big/sugar daddies. the stomp is not bad either. but the mothership is super soft.
i would definately stay away from anything with a foam core, that shit looses it's stiffness over time, so i'd recomend the ak launchers and any o the fat atomics