Power weapon
Power weapons are a type of weapon in Warhammer 40,000. Power weapons look just like normal melee weapons, but what makes them actually useful is that they are sheathed with an energy field surrounding the blade. This energy field can in turn slice through even the toughest of armor.
Types of Power weapons
Power Sword
One of the rarest of power weapons. Considered more flashy than the chainsword, but just as deadly, Power Swords are usually granted to high ranking members of the Imperium of Man, such as Imperial Guard regiment commanders or Space Marine captains. Most of the Primarchs who had swords used Power Swords.
Power Axe
More readily available in the armoury than Power Swords, Power Axes are double-bladed axes with their edges sheathed in energy. One would think that having technology available to them would better allow them to produce other types of power weapons, but the Adeptus Mechanicus are idiots like that.
Power Fist
One of the most iconic weapons of 40k, Power fists are massive gauntlets which are encased within energy when activated. They are intended to be worn with Terminator armour, but frequently you find people without power armour wielding power fists. The God-Emperor of Mankind had a power fist on a left hand, which he used to famously put Leman Russ in his place. Russ later said that the subsequent headache was from the drinking contest they had.
Orks, in their looting tendencies, have taken to mimicking power fists as power klaws, which are like power fists except that they have three digits and end in pinching talons.
Power Lance
A weapon used almost exclusively by the White Scars, Power Lances are energy sheathed lances which the White Scars use in charging their opponents on their bikes. You can imagine the results.