Seeing all the giant Scorpions running around Moonbase recently, here's a few of my own. First up the Tomy Zevle 'Zargam' or Deathpion. A 1/24 scale Zoid-like beast, the Zevle line was briefly released in 1992 and featured articulated 3" figures, rather than the tiny golden pilots. It may not have been a huge success, but the Deathpion is an amazing piece of robotic design. Battery powered, it scuttles forward, claws snapping and tail tail twitching.
At around 14" long, its well detailed and as with all Zoids models, extremely well made. This model has been built as a kit and painted professionally. (not by me, I hasten to add).
The resurgence of the Zoids line in the mid 2000's brought new life to the series and a wave of new models. One of the best must be the sea scorpion 'Death Stinger'. In standard Zoid scale, it is piloted by the gold android figure, but is roughly the same size as the Deathpion.
It has similar action, walking forward with claws snapping and tail moving. There are multiple folding fins and blades and the battery pack is disguised as a heavy dual gauss cannon on the back.
The head armour flips back to allow access to the cockpit and shows the red eyes and scissor jaws more clearly.
Finally from the Transformers film comes the Scorponok, as seen whizzing around the desert, giving the hapless Marines a hard time. Unlike most modern Transformer toys, it does not convert to a robot, but does have a complex gear arrangement, which causes the claws to spin as it is pushed along. The tail fires a harpoon too.
Although not strictly a scorpion, and more akin to a lobster, the Mattel Atlantis 'Leviathan' from the Disney cartoon is a modular toy which can break down into smaller vehicles too.