Vantec SSPS105 Servo
These are Seiko servos. They have 27 ft/lb of torque! That's over 5180 in/oz of torque. You'd have to gang up over 123 standard servos to get that power. It's $524 at Vantec.com. They were made for the RPV's and UAV's. I had an idea to use these to fly an experimental plane via remote control. They could definitely handle it. They weigh 27 ounces each but what a beast.
I bet that large delta model could be flown with these servos.
Vanteck SSPS050 servo
They have 690in/oz of torque and are $194.
Of course my favorite monster servo is this one, it's only $40 and has 325 in/oz of torque.
Hobbico CS-80 Giant scale servo
I used three of these to convert my self-propelled lawnmower to RC operation. You can see it here:
Wingspan99's RC lawmnower