Book of Mario is a text-hack of the Paper Mario (Nintendo 64) created by Fatguy703 and his fans. The text within the game is produced by oscillating translations several times (with Google Translate) to change the dialogue, creating a very different plot from the original game. The game also has a new badge added, which was only obtained via hacking.
Banjo-Kazooie: The Bear Waker is an unofficial Banjo-Kazooie (Nintendo 64) ROM hack/mod. The game features Outset Island, from The Legend of Zelda: The Wind Waker. Banjo and Kazooie need to explore the area and find collectibles while looking for Link, because he is missing and the King of Red Lions is waiting for him.
Banjo-Kazooie: The Hidden Lair is a passion project by Daveyx0 and Oldum77. It shows a possible continuation of the series, with possible events after Banjo-Tooie. It features a new area of the original Grunty's Lair that acts as the main hub, called the Hidden Lair.
Super Mario and the Cursed Castles is a major ROM hack created by Foxen, having 121 Stars (as of v1.01) to collect spread over 15 courses and a few extra levels. It is notable for two reasons: The lack of any true "secret" levels (all Stars are located in levels that are easy to find), and the sheer size of the game's levels.
Super Slide 64 is a Super Mario 64 mini hack made by Pieordie1. Race over 20 slides to collect 48 stars.
The main mechanic of the game is to slide through the levels.
Majora's Mask Randomizer is an application that randomizes item locations, music, and more for Majora's Mask, presenting millions of combinations and new ways to replay the game.