Genesect

Genosekuto a /-type Generation V Legendary Pokemon. Genosekuto was an ancient bug that was captured and experimented on by Team Plasma. They turned it in to a soulless and heartless robot with pure metal armor skin and a big super cannon. The cannon move, Techno Buster, has chips called Cassettes that can change its type. There 4 types of Cassettes and the types are Fire, Water, Electric and Ice. The Cassettes are called Blaze Cassette, Aqua Cassette, Lightning Cassette and Ice Cassette.

Pokedex entry
A bug Pokemon from ancient times, reconstructed from team plasma. They advanced the gun on it's back