Reaver's Blade is a tier 2 epic Two-Handed Slashing weapon. It is preceded by the tier 1 epic, Doomblade.
Void Core: 22
Max Level: 75
Max Att: 262
Max Def: 0
Max Dmg: 337
Reaver's Blade makes the Samurai and Templar actually viable damage threats. This is in part due to its stats being favorably weighted toward pure offense. The other reason is because of Reaver's Blade's incredible stats and bonus effects.
It is the highest damage weapon in the game. This makes it especially powerful with the Templar's passive Wrathful. Furthermore, the bonuses are top in class. 3% crit chance as well as bonus crit damage are both decent together. Even better, faster cooldowns is always a great bonus.
Most of all, though, 20% armor penetration is arguably the most powerful bonus in the game. Considering the standard tank has 35% armor from a max T2 plate armor, plus 20% base, and another ~25% from skills, it's expected most tanks will have up to the cap of 80% armor. Reducing 80% armor to 60% armor doubles all damage dealt—not just the weapon's damage, but also the base damage in the skill. In this specific context it would be even more powerful than a double damage-type bonus.