A huge amount of different connectors are used in this hobby. At EuroRC you will find a very large assortment of different connectors, with bullet connectors of different sizes, Tamiya, Traxxas (TRX), Deans (T), XT60, XT90, EC3, Futaba, BEC and many more connectors in stock.

Few examples to help choosing the right connector for your purposes.

JR/Futaba Traditional 3-pin "servo"connector -> for servos and other electronical accessories.
JST 2-pin light current connector -> Popular in RX battery and other low current applications.
Tamiya -> Popular standard RTR connector - Recommended for NiMh batteries in 7,2-8,4V systems.
Deans & T-Plug traditional upgrade to replace Tamiya connector - Needs soldering - Suitable for 2-4S systems.
Traxxas & TRX -> Traxxas connector - Needs soldering - Can handle high currents if needed - Suitable for 2-8S systems in 1:10 to 1:8 scale.
XT30 connector with 2mm bullets - sturdy connector - Needs soldering - Good for powering servos and connecting RX batteries.
XT60 & EC3 -> Connectors with 3.5mm bullets - Needs soldering - Good option for main connector in 2-3S systems in 1:10 scale.
XT90 & EC5 -> XT90 (4.5mm bullets) and EC5 (5mm bullets) are both very sturdy and robust connectors - Both needs soldering - For 4-12S systems in 1:10 to 1:5 scale.