Goblins will do anything for profit and show very little regard for ethics, as long as it is seen as profitable they will gladly exploit it and can be rather backstabbing as a result, though they are avid traders and are willing to help others if they feel they will gain a reward.
Goblins can also be vindictive and acrimonious, so they can have a rivalry of sorts with Gnomes, especially when it comes to Engineering - with Goblins preferring destructive and often highly explosive gadgets while Gnomes prefer outlandish inventions.
Goblins don't really have a code of honor but do seem to have some kind of structure to their society as they are ruled by powerful Trade Princes, which further empathizes the importance of trade in Goblin culture.
Like all races Goblins vary by individual to individual and some are downright malevolent, though on the whole they tend to be greedy and scheming rather than outright evil - unless they see a means of exploiting someone, at which point they can become antagonistic: such as how they often deforest massive areas of land in their quest to profit, uncaring of the damage it can cause to the environment.
Prior to the Cataclysm expansion, Goblins were considered the most notably "neutral" race in the game, as the majority were generally independent NPCs who would offer work to both the Alliance and Horde, most affiliated with the "Steamwheedle Cartel" faction, while others, such as the Venture Company, were enemies. With the release of Cataclysm, Goblins became a playable race and part of the Horde, which further reinforced their role as counterparts to the Gnomes. The playable Goblins belong to the "Bilgewater Cartel" group, which is led by the most evil Goblin of them all, the cruel, violent, and treacherous leader named Trade Prince Jastor Gallywix, who is hated even by the majority of his own people.