Precisely, I like featherweights because I should be able to do most of the construction on my bedroom windowsill

Money though...not speaking from experience here (as always :P) but it seems that if youre particularly resourceful and have the right sort of stuff lying around you can build heavyweights for next to nothing, get old broken wheelchairs from dealers and adapt the motors/batteries/controller for your use, its how a lot of series 1/2 robots did it anyway and allegedly some of them cost next to nothing.

But I digress, favourite feather at the moment would probably be Crumple Zone, that thing looks...scary, among other things...awesome but scary.