The Millenium Items are a group of seven Ancient Egyptian artifacts with special powers. So far, only six items have been revealed.
2. The Millenium Eye, owned by Maximillion Pegasus. The Eye gives Pegasus the ability to see into other people's minds, and to move duels into the Shadow Realm. It also can fire Ancient Egyptian Lazer Beams.
3. The Millenium Ring, owned by Ryo Bakura. Yami Bakura resides within the Ring. It seems to contain the most abilities of all items, allowing Bakura to bend time and space, place souls into Duel Monster's cards, detect Millennium Items and gay people (through use of the arrows), and fire Ancient Egyptian Lazer Beams.
4. The Millenium Key, owned by Shadi. Shadi uses this to see into the minds of others (effectively making it a ripoff of the Eye). It can also be used to allow the user to travel inside the person's mind, revealing their memories.
5. The Millenium Rod, owned by Marik Ishtar. It appears to contain the spirit of Melvin, who is Marik's imaginary friend from his childhood. The Rod allows Marik to control the minds of anyone who is named Steve, which is a major downside to many of Marik's plans.
6. The Millenium Necklace, owned by Ishizu Ishtar. The Necklace allows Ishizu to see into the past and the future, though she doesn't seem to use its Precognative abilities to any useful extent, forcing her to be late to most occasions and miss important details of giving Seto Kaiba the card Obelisk the Tormentor (specifically, that he would never give it back to her) as well as bring up past events that were deemed unimportant, such as when she brought up events in Yami's childhood. She can also use it to break the fourth wall.
7. The seventh Millenium Item is the Millenium Scale, which is also owned by Shadi. It is used to weigh the evil in one's heart. So far it is unknown what it's other abilities are.