I found a cheap servo that works really really well.
I have everything from cheap $2 servos up to $100 titanium gear monsters and i recently bought some 8 dollar servos from Hobby King for arm servos.
They seem to perform really nice, lots of torque, got metal gears, can handle 5 to 7 volts and they feel like a much more expensive servo.
They are for the price the nicest servos ive ever found.
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SG 5010 Servos
At about $6 a piece, but you can get them a bit cheaper. No metal gears but tons of torque:
Stall Torque (4.8V): (8 kg/cm) (110oz/in.)
Stall Torque (6.0V): (11kg/cm) (156oz/in.)
I haven't had a single problem with them yet. Only problem is the long ship time from China.