Pikmin

• Call in backup Pikmin
• Figure appears in-game and can be collected to gain energy points
• Make a random other figure appear in-game to be collected

Community-reported

• Unlock a Pikmin-themed Mii racing suit

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

• Unlock a character-based Mystery Mushroom costume

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

From NintendoSource