After reading through this, I have to say there are really good ideas. Actually very difficult too choose one. I like the Magnetron, because I was abusing that thing a bit too much...
(I did once build 12 of them at one spot not far away form the enemy base... and the result was hilarious! I never ever have seen a GC walk multiple times faster than the fastes plane can fly... or you use the push function whitch is even better if the enemy can´t get out of his base.)
Ok enouth of that crap, let´s look into something really seriously "Gameending":
Give the Scathis a EMP weapon sounds the best solution, but I want to achieve two things with it.
-First, make it completely and totaly redicilous
-Second, make it well balanced
I think I can´t do this alone, but here are my Ideas:
First, make it able to shoot EMP Nuke projectile [almost no damage, but stuns everything for quite some time (10 sec. mabye?) with AoE of a real Nuke + 40km range + real Nuke explosion animation and sound]
Second, since it is a "Gameender" make the projectile as redicilously expensive as it would be OP, like to shoot one you need 100.000 Power
So to Sum this up:
Give Scathis an additional firemode that requires a ludicrous amount of Energy to load, but now just Imagine how funny it is when you have enouth [E] to make it rapid fire
I guess it ends the game very well, when your "target" can´t simply do anything
Of course some additional finetuning should be done to see and mabye get it into a Balance Patch (for example more E cost). I hope you like my Idea.