If ever a sound was associated with a particular class, it's the sapper. Quite simply, sappers love to blow things up. However, unlike many goblin tinkers, they don't necessarily like the idea of killing themselves in the process. No, to a sapper, the fiery blast of a good explosion is a form of art unto itself. Some spend a great deal of their lives trying to find new and interesting ways to generate beautiful, classy explosions. Sappers are experts in all sorts of explosive devices, from small firecrackers to powerful seaforium charges capable of blowing holes in thick castle walls. Even when they don't have a prepared explosive available, a good sapper can put one together out of whatever natural materials he can find lying around.
Goblins are likely candidates for this class, since goblins like making things go boom! Gnomes and dwarves also make able sappers, with humans following close behind. The Horde made heavy use of goblin sappers in the Second War; indeed, goblin sappers were a key aspect of the Horde's strategy. Thus, the Horde knows how effective this class can be. In an adventuring party, a sapper often takes the role of a rogue or ranged combat support. He disdains typical rogue skills such as opening locks and disarming traps - he simply destroys such obstacles. When a battle erupts, he stays behind the lines, lobbing bombs into groups of enemies or employing fire-based technological devices to pick off more determined foes.
A sapper generally takes great care to avoid harming himself; but still, he spends so much time around explosives that accidents are bound to happen. As a result, his body gradually becomes covered with a layer of tough scarring that protects against fire.
The sapper has learned new tricks to increase the yield of his explosives. Any grenade, bomb or other technological device he creates that deals explosive fire damage deals an additional damage per die.
The sapper is an expert in both the crafting and use of explosive devices. Any sort of bomb or grenade — basically anything that blows up — is his specialty.
A sapper can attempt to build small explosive devices out of whatever materials are available. Even in the midst of an untamed wilderness, he can usually locate certain plants or minerals that, when mixed together, become something flammable.
The sapper is an expert on the delivery of explosive devices from a distance, whether employing any thrown or launched explosive device (such as a mortar).
The highly skilled sapper has transformed explosives into works of art. He can deploy a perfect blast — a thing of beauty (at least to himself and his allies). He can use this ability with any explosive device — as small as a grenade all the way up to massive wall-cracking charges — but he must prepare, set and activate the device himself. Doing so takes twice as long as normal for the device in question, but if it is successfully set off, the explosive deals the maximum possible. 
- Main article: goblin sapper
A great number of sappers - primarily goblin sappers - perished during the last war, mostly as a result of their overzealous use of too many explosives at once. Those who survived have become much more focused in their art, preferring precision to risks. Generally, the older a sapper is, the more careful and cautious he is - and the more respect his associates give him.
Sappers are engines of destruction; when the Alliance needs a structure removed from the battlefield, a dwarven demolition team is sent to blow it away. Sappers invite bloody death (and hearing loss) every time they go into action, but the sight of a Horde gatehouse collapsing into a pile of rubble is well worth such risks. 
- Main article: Dwarven Demolition Squad
Cheerfully striding onto the battlefield is a team of odd dwarves, scarred and blackened faces, a mace in one hand, a pistol in the other, hauling kegs of powder strapped to their backs. They seem to ignore the rest of the field. The sapper’s tactics focus on delivering large amounts of gunpowder to a target and using his skills to destroy it. They are aware of the surrounding battle only as it concerns their ability to reach their target and have enough time to set a charge and escape.
This team likely later evolved into the Dwarven Mortar Team.
Sappers in WoW
- Clockwork Sapper - Ulduar
- Dark Iron Sapper- Loch Modan
- Dark Iron Demolitionist - Wetlands
- Gan'arg Sapper - Hellfire Peninsula
- Goblin Sapper - The Storm Peaks