I'm voting for the mech thing. Sure it may be overused and somehting you've all seen before, but thats why its so great. We can all work on somehting we are familiar with, and with a project like this (with the slim chance of success that it has) that's a very good feature.
People still love the idea, even though it's been used so much.

As for the mallows and pencils, it sounds like a nice concept, but if it will work id an entirely different story. We're going to make a game about this, with a (hopefully) complex storyline the player can follow through to keep them hooked on the game. I dont see that happening with the other two designs.

Besides, drawing robots is cool

You have my vote, and my cooperation no matter what this turns out to be, let's enjoy this