Boo

• Unlock the Chain Chomp weapon

Community-reported

• Unlock a special costume

Community-reported

• Figure appears in-game and can be collected to gain energy points

Community-reported

• Make the map show the locations of up to three hidden Boos in the mansion that have escaped capture

Community-reported

• Receive a helpful item

Community-reported

• Receive a stamp and equipment for the main quest
• Receive a stamp, equipment, and a special ability for Bowser's Minions mode

Community-reported

• Play as or receive bonus from this character, depending on the mode
• Unlock a Boo-themed background in Boo's Block Party

Community-reported

• Minigame Island: If you land on an amiibo space, use to receive coins / Use to revive your character once

Community-reported

• Receive a random title or avatar item, up to five times a day. Each amiibo can be used once a day.

From NintendoSource

• Receive a Super Star in both Super Mario 3D World and Bowser’s Fury.

From NintendoSource

• Change Bellabel Park flowers and decorations to a character theme; receive an item when scanned during a course.

From NintendoSource

• Receive a helpful item depending on the character

Community-reported

• Unlock the character's shiny sticker

Community-reported

• Receive a Spirit of the character

Community-reported

• Receive a sketch of the character from Wario which can be exchanged for in-game coins

Community-reported

• Unlock a character-based Yoshi yarn pattern

Community-reported

• Unlock randomly assigned three-minute NES or SNES game scenes. Subsequent scans change the scene.

From NintendoSource