There is a 50/50 chance that a LAW will one shot a Fleshpound on any difficulty, we think it has to do with landing some nades at it's feet and then hitting it with the LAW. The grenades themselves don't need to explode, but there seems to be this weird bug that allows you Giblets a FP with one shot.
Some say because FP's take extra explosive damage, but that doesn't make much sense considering grenades should be explosives.
This theory was tested on suicidal Tao and hard Tao. Great map for lining up LAW/Grenade combos.
6/9 FP's exploded, needless to say the guy with the LAW died a few times.
Too much human error possibility to make a decisive conclusion. There may be a purpose to it yet!
(Can you tell if we're bored yet >.>)