Forbidden Mountain

Tarantulas looked like a gigantic dork in season 1, so you can imagine my surprise when his transmetal form looked AWESOME. I mean LOOK at that thing. It's so badass, and fit his character way more. His revealing as a secret Predacon agent (spoilers) gives all his little experiments and machinations a much darker and cooler flavor. I'm bummed he didn't survive longer, he could have been a worse villain than Megatron in the long run (although in post-BM comics continuity the Vok do bring him back, which I support fully).