Current sculpts only?
A lot of 'mechs that had one-piece sculpts got re-sculpted, and now have separate arms (e.g. Dragon, Grasshopper, Zeus, etc.). In many of these cases, the plastic Lance-pack versions are still one-piece.
In any case, I think the old once-piece Cyclops sculpt is still the current sculpt.
Also:
Assassin
Cataphract CTF-1X Nope
Urbanmech
Clint
Exterminator
Whitworth
Guillotine (I think?)
[Edited to add more options, after a quick review of the IWM catalog]