Tactical-Life.com takes a look at 7 megapistols. Hybrids of rifles made into the pistol category. The obvious benefits are high powered and no Class 3 ATF license and tax stamp. Most of the 7 are a form of an AR pistol.
Here are the ones that stand out.
CzechPoint SA Vz. 58 is an interesting option. Not quite an AK as it is based of the SA Vz. 58 but chambered in 5.56.
According to author Doug Larson:
The AK-47 incorporates a rotating bolt in a bolt carrier that is permanently attached to the gas piston, and the bolt has two locking lugs that engage recesses in the trunnion or receiver to solidly lock the bolt in battery. The vz. 58, however, uses a bolt that is locked into battery by a camming block that drops into two slots cut into the receiver—in a manner similar to the locking mechanism of the P.38—and the gas piston is a separate piece that is not attached to the bolt carrier. While the AK-47 uses a long-stroke piston, the vz. 58 piston is a short-stroke design that imparts a sharp blow to the front of the bolt carrier, sending it backwards for the extraction stroke. The carrier is then propelled forward by a recoil spring, permitting the bolt to strip a fresh cartridge from the magazine and feed it into the chamber. In the meantime, the piston is returned to its forward position by a coil spring.
I find the MasterPiece MPA930 9mm an interesting choice. I do not see much benefit to a Mac10 styled pistol over, say, a Glock 17, with red dot and 33 rd magazine. I think they should have added the KRISS Vector SDP pistol instead of this.
Tactical-life also included the Mossberg 715P .22LR
I would not consider this a “megapistol” but more in the category of a fun range toy. It doesn’t catch my fancy but you may have a different preference than me. 25 rds of .22lr just doesnt seem like much when compared to my PMR-30 with 30 rds of .22WMR.