This is the most mini servo. Only weights 9 gram and gives you a 1.6kg.cm torque. Pretty strong regarding its size.  Suitable for Beam type robot.Specification

• No load speed: 0.12 seconds / 60 degrees (4.8V)
• Stall Torque: 1.6 kg / cm (4.8V)
• Operating temperature: -30 ~  +60 degrees Celsius
• Dead Set: 7 microseconds
• Operating voltage: 4.8V-6V
• Working rurrent: less than 500mA
• Cable length: 180mm
• Size: 22mmx12.5mmx29.5mm
• Weight: 9 grams