- 5e

https://www.youtube.com/watch?v=dv27NlqAOHg

Broom of Flying

Amulet of the Planes

I'd argue the "familiarity" text of this item requires the player to have been at the location before and spent a fair amount of time exploring/learning about it. This might be useful as a tool for a hidden location the player could retreat to or fast travel back to previous locations.

Instant Fortress

Cloak of Invisibility

Blindsight, Tremorsight, etc. bring this back down... Certain locations might have anti-magic zones.

Ring of Wishes, Efreeti Bottle, Luck Blade (Wishes)

Unexpected wishes ruin games, foreshadow the item for at least a few sessions (listen to how they talk about it for a few sessions before awarding it)

The Deck of Many Things

Let it break your campaign.

Equipment and Magic Items for Wizards (not necessarily game breaking)

https://www.youtube.com/watch?v=zg5UjitJT8c

Weapon of Warning http://dnd5e.wikidot.com/wondrous-items:weapon-of-warning

Rod of Absorption https://roll20.net/compendium/dnd5e/Rod%20of%20Absorption#content

Mundane Items: Explorer's Pack (instead of Scholar's Pack)... Component Pouch (over Focus?!), Bullseye Lantern, Ballbearings, Caltrops Spells, Staves, and Wands - if they are on the wizard spell list, you can scribe it into the spellbook

(Component Pouch covers multiclassing)

https://www.youtube.com/watch?v=nk1Up4hXUko

Not Game Breaking -- But good items for low level parties