For my current setting, there will be super robots of ludicrous proportions strutting about as though they own the place (which in all honesty they actually do). So, being so nonsensically powerful, they need a suitably nonsensical power-source.
However, I dislike creating green-rocks to use as a fuel, as it tends to get out of hand quickly as I start fleshing out its properties, as such, I was thinking of using something that, at minimum, must be able to exist in our universe.
So, the question is, all limits of current technology aside, what would be the most powerful portable energy source available? Would it be like a miniature sun? My friend had previously suggested something he called a 'Binary Black Hole Generator', the science of which eludes me.