Titans Return Megatron
Head and tail: Constructbots Deadend (heavily modified)
Lower arms: Movie Scorponok
Tail end: Movie Scorponok
Side pieces: Lego 4 peg piece

I went ahead and got rid of the scorpion legs and added a 4 peg Lego piece on both sides. I redid the tail and added the movie sharp end piece to the tail as a stinger. As far as the head, took some old head pieces, and a RID Megatron foot piece and modified it into a scorpion-like head. In the end, I give you Scorponok.

He does have a city mode. The scorpion stinger doubles as a cannon. The scorpion claws double as tunnels into the city....kind of generator like mode.

The missle packs on his shoulder are from dollar general robot packs.