Continuing the trend of weird swarms: the shredstorm.
14 construct RHD are generally a bad sign, and the ability scores aren't very impressive either (22 dexterity is the only boosted stat in a sea of mediocrity). 90 ft. fly speed is impressive, and +8 natural armor is nice, but apart from that the chassis is hardly useful. The shredstorm's swarm attack deals 3d6 regular damage and 2d6 electricity, which is more than certain other swarms get (lookin' at you, shimmerlings), but still not a lot.
Its special abilities are somewhat interesting: Penetration basically turns the entire swarm into a DR-ignoring, incorporeal-hitting, adamantine weapon, which is nice. Lightning Bolt lets the shredstorm duplicate the eponymous spell at CL 14, but it also cuts its electricity rider damage in half for hours. The real question is if the ability itself can be used at-will or once every 2d6 hours: the second would make it mostly forgettable, while the first turns the shredstorm into an okay-ish blaster with good defenses.
Considering all of this, I think the shredstorm is a -0, though it's a significantly better one if its ability can be used at-will. Even so, -0 for now: do discuss.