There are many plugs to choose from in the RC world. These are dependent on power handling requirements, resistance, and own personal preference. Using one type and is the easiest way to swap different batteries from various applications and ease of charging.
The most common are:
This is a small power plug rated for up to 5 amps of continuous load. It is used on smaller battery packs for powering receivers of nitro / gas RC applications, small park fliers, and micro electric helis.
Deans Ultra Connectors
These are a very popular connector type (also called "T" connectors) on electric RC cars. This is a high quality low resistance plug. They are rated for up to 50 amps of continuous load.
EC3's are becoming very popular as they use true "bullet style" connection pins and are rated for up to 60 amps of continuous load. Most will agree bullet pins make for the best possible connection when dealing with high current applications due to a larger surface contact area. Common for Losi vehicles.
These are a longer version of the EC3 and because the bullet pins are longer (5mm) they have an even greater surface area for contact. EC5's are rated for up to 120 amps of continuous load. Another common on larger scale Losi vehicles.
HexTronik XT-60 Connectors
XT-60 connectors are popular in plane and heliapplications. Like the EC3 connectors they use gold plated bullet pins and have a slightly higher 65 amp current rating.
These are lower amperage connectors once very popular, especially with the electric RC car, truck, and boat crowd, but since high amp LiPo's have entered the scene, Tamiya plugs are used less and less. You still will find them used for powering smaller models and some types of nitro starting systems.
As the name suggests, Traxxas battery connectors are used exclusively on electric Traxxas RC vehicles/boats but can be fit to any high current application up to about 100 amps. These are a good connectors are are greatly growing in popularity.