The Goblin is the fastest ground unit in the game.
The Goblin's first target is Resource Buildings, making them the ideal troop to deploy if your primary concern from a raid is collecting resources. In fact, there is a whole strategy involved around their use, named milking. Some good strategy forum threads can be found here.
Because the nature of the character is to attack Resource Buildings first (ignoring all defenses) they can be vulnerable to attack and should not be deployed without another type of troop (such as the Giant or Barbarians) as a meat shield.
An alternative to Wall Breakers is the Jump Spell, which helps guide Goblins over the walls and directly into the riches inside, however this is much more expensive.
Like Archers, the Goblin's greatest weakness is splash-damaging structures (i.e. Wizard Towers, Mortars). Most Wizard Towers and Mortars can kill Goblins in one shot. To combat this, send in Goblins in waves rather than spawning them all at once. Alternatively, you could send in Giants and Barbarians and let them serve as distractions while the Goblins get the resources.
Another good strategy is to place a couple of Goblins after the defenses are destroyed to help clean up any remaining buildings before time runs out. Since they are fast, they can speed over to buildings far away from each other. And if there are resources in the center, the Goblins will go right to it and ignore the other buildings.
Goblins are excellent at triggering Traps (especially Bombs), as their movement speed can allow them to get out of range before it detonates. This is especially helpful in the Single Player Campaign where there are often a large number of Bombs in predictable places.
You can also spawn Goblin hordes, for their attack speed and power can destroy many buildings. When all resource buildings have been destroyed, they will attack anything.
Goblins are usually not viewed as a good troop for getting Trophies, however they can be useful in small amounts.
For example, if you are doing a revenge and you think your units might go to the sides instead of into the middle because of resource buildings outside the Walls, you can use 5 Goblins per resource building to clear the way for your troops so they go in the middle.
Also, Goblins can be useful at the end of attacks. If you didn't get to 50% and all your other troops died you may be able to use Goblins to destroy a few mines and collectors to get you over 50%.
If your main attack missed the Town Hall but destroyed most of the defenses nearby then goblins are perfect for picking up another star for the attack.
Goblins are a great choice as clean up Troops for War attacks for Town Hall 8-9 players since majority of the leftover buildings are Resource Buildings which makes Goblins extremely effective to prevent time shortage.
Although generally not viewed as the best defensive troop, Goblins are still useful as Clan Castletroops. As there are no resources to target, Goblins will attack the enemy very quickly compared to the other troops.
Goblins have the highest damage of any of the low health troops and can engage the enemy units quickly due to their fast movement speed. They are particularly proficient at taking out small numbers of Giants on defense.
The Goblin undergoes a significant change at level 5.
Upon first receiving the Goblin his appearance is that of a small, green creature with large pointy ears, red eyes with green pupils and a red-tipped nose. The Goblin wears red suspenders, brown pants and shoes. He also has a large sack, ostensibly for carrying resources stolen from your enemy.
At level 3 & 4, the Goblin’s bag receives light brown stripes on the sides of it.
At level 5, the Goblin’s bag turns all light brown and he gains a red mohawk.
At level 6, the Goblin gains a red leather cape and a golden necklace.
At level 7, the Goblin's mohawk turns bright orange and becomes squared off at the back.
Goblins are the main antagonist in the Single Player Campaign, despite the fact that you can train them as part of your army. Your own Goblins seem to have no compunction about attacking their NPC brethren.
Oddly, the two CPU Goblins spawned during the tutorial ignore your Gold Mine and go straight to the Cannon.
When you tap on the Army Camp the Goblins stationed there all turn and look to their left for a brief moment.
You can have a maximum of 240 Goblins at one time in a complete set of fully upgraded Army Camps. This number increases to 275 if you include the 35 that can fit into a level 6 or higher Clan Castle. On the battlefield, you can clone an additional 80 Goblins with two fully upgraded Clone Spells.
Goblins have the highest damage-per-second of any troop on a per-housing space basis (52 DPS at level 7, slightly higher than the level 7 Wizard).
They are the only ground unit known to be faster than a Spring Trap. This does not mean they are not affected by the Spring Trap. For example, if there is a large group of Goblins running over the Spring Trap, the front Goblins will release the Spring Trap, run quickly over it, thus causing the Goblins in the back to be sprung by the Spring Trap.