For those on a budget and want something better then the basic plastic gear servos, the Blue Bird range is a great Option.
In my back up 1/10th touring car I'm using a Blue Bird BMS-631MG Super Fast Servo (Metal Gear).
Stats are.
Weight: 46 grams / 1.62 oz.
Dimensions: 40.5 x 20 x 41.2 mm / 1.60 x 0.78 x 1.54 inch
Torque At 4.8V: 5.0kg-cm , 69 oz-in
Torque At 6.0V: 6.2kg-cm , 89 oz-in
Speed At 4.8V: 0.10 sec / 60° at no load
Speed At 6.0V: 0.08 sec / 60° at no load
Compared to my Savox 1251MG low profile servo, the performance is not that much different. It's a little bigger, heavier and not as much torque but for $15, it's a heck of a lot better then the plastic servos that come in the cheaper radio kits.
Cheers
Rob.