The S6170 is a good solid standard digital servo that is lightweight and offers good performance in most 1/10 2WD applications.

The S9110BL and S9120BL servos have been designed to give 1/5 enthusiasts huge torque and brushless motor precision, taking their driving experiences to a new level.

Micro Metal Gear Servo - SX107 - Spektrum

The EcoPower WP110T Cored Waterproof "High Torque" Metal Gear Servo is a great choice if you are looking for an affordable, waterproof RTR upgrade.

The EcoPower WP120T Coreless Waterproof "High Torque" Metal Gear Digital Servo is a great choice if you are looking for an affordable, waterproof, high voltage upgrade.