Maulers were interesting in theory, but not especially useful since they didn't miniaturize as well as plasmas or disrupters, and couldn't be fitted with autofire mods. Their always hit bonus was kinda meh too, since they were late game tech and by then you couldn't miss anything short of a cloaked alkari frigate.
Converters were very nice, but not for combat - the space/damage ratio was just too low. I considered them a resource enhancing device myself. Assuming there are at least 2 planets in a system, blow one up, take the other, reconstruct the one you blew up into a large barren world, give the other to an enemy, blow that up and repeat.
It was the only was to improve planetary size, or get rid of the ****ing toxic worlds.
Oh, and I habitually blew up other races homeworlds. But that was more a political move then a resource one.