So, let's compare that to what I bought at Historicon.
As far as Martians go, all I purchased was a box of High Martians (the flying guys) [RAFM]. My son also bought some Mage Knight cannons that will probably be pressed into Martian service, as they are sort of primitive looking and bulky and just look 'right.'
For the Masked Minions, I purchased a 4 figure gun crew [Parroom Station]. I also bought a Smoke Launcher [Parroom Station] for them to crew. The gun may be used by others, of course. And it may not always be a Smoke launcher. Suppose I need rules for the poisonous cloud that it fires off. Maybe a blast template that wanders with the wind? Green-sprayed battening on an old CD base? Bears thinking about.
For our third place contestant, the Germans, I bought infantry and a massive artillery piece. Again, the artillery piece could be used by anyone, really. It is the Steampunk Cannon [JR Miniatures]. Having a stubby, mortar-like appearance, I also want to make a barrel extension for it (removable, of course) so that it can be made to look like a big fortress piece. Shouldn't be too difficult, as the barrel of the original mortar is tapped quite deeply. I'll explain my idea for it when I get around to doing it. The infantry I chose were the Prussian infantry of Parroom Station.