I have 3 ideas (2 of which are technically from manga but I don't think that particularly matters).
1: LIEGE MAXIMO. And no, not the piddly Loki Ripoff from the Covenant of Primus. I'm talking the Arch-fiend from the very last page of G2 that makes Unicron himself tremble with fear. You know, this guy:
Just look at this glorious motherslagger. Just LOOK AT HIM. Tell me you don't want a Titan class toy of this mountain of monstrousness. Those claws, those Giger-tubes, that HEAD...
Liege Maximo. It shall be so.
2: Super Megatron. From the Battlestars manga IIRC, this design was just pure badass. Transforming from a robot into...a robot with more guns on it into a space battleship into what seems to be some kind of giant handgun of DOOM. I know absolutely zero about Battlestars, but boy oh boy does this design deserve immortalizing in plastic.
3: Kiss Players Legion. Yes, they were creepy as all hell, spawned from the worst
thing to ever grace Transformers and were basically just Alternators Windchargers with new heads, but they were so gloriously disturbing that part of me kinda wants one (preferably in CHUG scale though). Honestly, if it weren't for the fact they were included alongside all sorts of other really, really out of order...stuff they'd probably be remembered as some of the most uniquely terrifying things in Transformers history. Maybe I'm biased because Alien is my favourite movie ever and as such I have a fondness for biomechanical, phallus-themed flesh-eating monsters, but I kinda feel like the Legion deserve to be something more than just a horrible footnote in a particularly loathsome chapter of Transformers.
No pictures because seriously, these guys are HORRIBLE. If Takara were to ever make toys of them (which given how poorly received Kiss Players was in Japan is highly unlikely) they'd probably have to make those tongues a little bit less obviously penile.