I am getting the AM-05 Megatron, and most of the reviews make it seem that his minicon, Gora, is only okay (with more than a few suggesting hooking Gora to PRiD Voyager Megatron). So, what alternate weapons would go well with Megatron? I am thinking of Energon Starscreams energon gun and sword combo.
I used Energon Ravage's cannon, painted black. It fits perfectly on the dorsal peg when Megs is in alt mode, and I use Gora's head piece as an adaptor/sensor pod to attach it to his arm in robot mode (plugged in a different way, Gora's head stays on the cannon in alt mode). It's small, but I kind of like the snub-nosed look, and the weapon certainly looks like it belongs on a Megatron. If you're looking for something that's close to Prime Megatron's cannon, modding the non-missile-firing half of Energon Arcee's bow to fit Megs' arm peg should look pretty close.