First up, we have Eviscerator by ama77what. A poseable mech with some Wolverine-like claws
Pico van Grootveld has a series of little "Raptors" which notable include a variant for both Blacktrons.
SupaFlyTNT has his Alienator V2. or as I like to call it, a very stompy mech. A very interesting take on the Blacktron 1 walker set. I feel it may have worked better without the arms.
And rounding this out is this nifty little transforming mech by 3D-foundry