Melta
Melta weapons are a type of anti-armor weapon used widely by the forces of the Imperium and Chaos, the Tau and Eldar also employ their own variants. Melta weapons work by super-agitating the air around it's barrel at a sub-atomic level that it heats up to the point where it's hot enough to melt anything (From power-armor to super-heavy tank armor) and shot out. The problem with melta-based weapons is that due to the super-high energy consumption and heat generation, it's only usable at short range. In comparison to the equally useful Plasma-based guns, Meltas are a lot stronger than Plasmas but have a very short range compared to them, but then again Meltas don't explode in your face on a bad roll. Though suited towards tank hunting, the Melta-based guns are good weapons for all-around attack, defence and infiltration, though it falls short in terms of range. Infiltration with this can take vehicles out of the fight before they even have a chance to fire their weapon...... is that how the baneblades were lost?
Imperial Meltagun Variants
Several variants of the meltagun are employed by the Imperium.
While the most notable variant is the Meltagun itself, there are several more types of Imperial Melta than this infantry-portable variant. The Multi-Melta is essentially two Meltaguns strapped together and supercharged, and in game terms only doubles the (already sucky) range and makes it a heavy weapon. This thing is still beastly and tears apart single targets, vehicles or otherwise, but are so huge that only Spees Mahreens and the Nuns with Guns can lift and move them by hand. It should be noted that Sisters of Battle love Melta weapons and, if given the chance, would only ever carry these things and Flamers.
The Imperial Guard felt left out, and decided to strap two Multi-Meltas together and show up the Sisters by making the Melta Cannon, an EKS BAWKS HUEG Melta weapon strapped to the Devil Dog Hellhound variant. This thing dumps small blasts worth of Multi-Melta statline upon anything it deems unlucky today, and is one of the best ways of dealing with Terminators. Some Witch Hunters get to use Inferno Pistols, rare Melta-pistols with a range so small you would have more opportunities to perform a root canal on your enemy in the middle of battle than use them. Still, those big-hatted pastors love nothing more than the look on your face when they one-shot your Leman Russ.
The Devil Dog light tank features the unique Melta Cannon: throwing a small Melta template to evaporate small areas at once instead of individual targets. Also, the Caestus Assault Ram uses this goofy Melta-drill doohicky to cut into spaceships and board them. Its also uses it to cut into every unit and evaporate them.
But the greatest of them all is the Titan Melta Cannon: twenty-five feet of FUCK YOU capable of evaporating tanks and fellow titans alike.
Filthy Xenos Variants
Eldar employ the use of Fusion Guns, Fusion Pistols and Fire Pikes. These things are like more snipery versions of Meltaguns, Inferno Pistols and Multi-Meltas respectively. Unlike the Sisters of Battle, these usually come stardard and in full-squad compliment. These things are also a great way for Fire Dragons to compensate.
Dark Eldar have the Heat Lance, a weapon that takes the best of the Lance and Melta weapons to obliterate any vehicle that gets too close.
The Weeaboos use Fusion Blasters, which are essentially dinky Multi-Meltas shining examples of the Tau technological superiority. It also comes in the fusion cascade variant, which has slightly lower strength, but can pretty much throw up a wall of melta streams on demand. It can only be used on the XV-9 Hazard Battlesuit, which is the Tau's close-quarters battlesuit of choice.