anything with a motor or a crank that is strong and reliable.
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The oodagat is the best because the motor doesn't get strained from rotating barrels. All barrels are stationary, while the triggerflipper is inside.
There actually aren't any great ones out there at the moment. They all run off of the same principle of having multiple chambers that rotate and fire themselves when struck, like a TR-18 with a motor and built in rams.