Dragon city Breeding Guides.

Breeding Guide

Terra	Flame	Sea
Nature	Electric	Ice
War	Legendary	Rare Hybrid

Lets Start with Terra Dragon

Terra + Flame = Flaming Rock or Volcano
Terra + Sea = Waterfall or Mud
Terra + Nature = Tropical or Cactus
Terra + Electric = Star or Chameleon
Terra + Ice = Snowflake or Alpine
Terra + Dark = Hedgehog or Venom

*Please note that you cannot breed Terra and Dark together for Armadillo dragon

Flame Dragon :

Flame Dragon Combinations

Flame + Terra = Flaming Rock or Volcano
Flame + Sea = Cloud or Blizzard
Flame + Nature = Firebird or Spicy
Flame + Electric = Hot Metal or Laser
Flame + Metal = Medieval or Steampunk
Flame + Dark = Vampire or Dark Fire

*Please note that breeding Flame and Ice to get Cool Fire Dragon is not possible here.

Sea Dragon :

Sea Dragon Combinations

Sea + Terra = Mud or Waterfall
Sea + Flame = Cloud or Blizzard
Sea + Nature = Nenufar or Coral
Sea + Electric = Storm or Lantern
Sea + Ice = Ice Cube or Ice Cream
Sea + Metal = Seashell or Mercury
Sea + Dark = Petroleum or Pirate

Nature Dragon :

Nature Dragon Combinations

Nature + Terra = Tropical or Cactus
Nature + Flame = Spicy or Firebird
Nature + Sea = Coral or Nenufar
Nature + Ice = Dandelion or Mojito
Nature + Metal = Dragonfly or Jade
Nature + Dark = Carnivore Plant or Rattle Snake

*You cannot breed Electric and Nature directly to get Gummy Dragon.

Electric Dragon :

Electric Dragon Combinations

Electric + Terra = Star or Chameleon
Electric + Flame = Laser or Hot Metal
Electric + Sea = Storm or Lantern Fish
Electric + Ice = Fluorescent or Moose
Electric + Metal = Battery or Gold
Electric + Dark = Neon

*Electric and Nature cannot be breed.

 

Ice Dragon :

Ice Dragon Combinations

Ice + Terra = Snowflake or Alpine
Ice + Sea = Ice Cube or Ice Cream
Ice + Nature = Dandelion or Mojito
Ice + Electric = Flourescent or Moose
Ice + Metal = Platinum or Pearl
Ice + Dark = Penguin

*Ice and Fire cannot be breed directly to get Cool Fire Dragon.

WAR Dragon :

War Dragon Combination List

War+ Terra = Colossal
War + Flame = Juggernaut
War + Nature = Red Woods
War + Electric = Tesla
War + Ice = Nightwind
War + Metal = Panzer
War + Dark = Dark Stone
War + Light = Elfic

*War Dragon cannot be breed directly with Sea.

Legendary Dragon :

 

These dragons are extremely powerful and useful in dragon city battles.
Since the July 2013 Light/War update, you will need to breed the pure or pure hybrids together for a chance to get the legendary dragons.
For example:
Pure + Pure Flame
Pure Ice + Pure Dark
Pure Terra + Pure Metal
Pure Electric + Pure Nature
*The new breeding time for legendary dragons are 2 days and 6 hours.

Rare Hybrid Dragon :

 

Rare Hybrid Dragons

The above combinations is what I would use to get the rare hybrids.
Firebird(Flame+Nature) + Star(Terra+Electric) = Gummy
Medieval(Flame+Metal) + Alpine(Terra+Ice) = Armadillo or Cool Fire or Soccer
Red Woods + Petroleum will give you a shot at Leviathan. There are also other combinations. Any War hybrid and Sea hybrid will also yield the same result. Poo is no longer a rare hybrid and is actually an exclusive dragon. Petroleum and Pirate dragon are now regular hybrids after the Light/War update of July 2013.
Photon(Light+Electric) + Rattlesnake(Nature + Dark) = Fallen Angel
There are also plenty of other combinations that will give you the rare hybrids.