Gear and weapons in Diablo 4 range significantly in rarity, all the way from common to legendary. However, there's also an additional type known as Unique Gear, with many options available to each class.
However, to get these Unique Items, you'll have to put in some heavy work and change your World Tier to reflect a much higher level. If you are wanting to grab these powerful items, here are the steps you'll need to follow.
How To Unlock Unique Items
Before you'll be able to pick up dropped Unique Items, you'll need to first make sure that you are currently playing the game on World Tier 2. If you need to change your World Tier, you can either do so from the main menu of Diablo 4, or visit the World Tier Statue in the city of Kyovashad.
You'll notice when you go to change your World Tier that Tier 3 and 4 are currently locked. In order to make these available to you, you'll need to complete the whole campaign of the game while in World Tier 2. Then, after you've done this, you'll need to complete the Cathedral of Light Capstone Dungeon and World Tier 3 and 4 will become available.
As you complete the campaign, head back to Kyovashad and make your way north of the waypoint. The Cathedral of Light Capstone Dungeon will be at the very northern part of the city, and will contain Level 50 enemies. After you've done this, you'll now have the chance to get Unique Items from drops when you switch over to World Tier 3 or 4.
Where To Get Unique Items
Now that you've unlocked the ability to find Unique Gear, there are a few different places where you can find the items from drops. However, keep in mind that Unique Gear is incredibly rare and might take some time and a bit of farming to actually come across one.
You can find Unique Gear from World Bosses, or within Nightmare Dungeons. It will take a lot of time to get these enemies to drop a Unique Item, though, so you'll be spending a lot of time with these bosses and repeatedly defeating them. It is worth the grinding, however, as the Unique Gear available in the game will be the perfect item for your endgame builds.