Infinite Arrows in Battle Quest
Fire your arrows while tilting the gamepad downward to have your arrows constantly reload, granting you infinite arrows.
100 Rupees (Stamp)
This stamp can be earned by collecting 100 rupees in The Legend of Zelda: Battle Quest mode. You can obtain rupees by defeating enemies, smashing pots, and cutting grass, among other things.
AI Mii Protector (Stamp)
This stamp can be had in solo mode of Pikmin Adventure. While playing solo, you'll be given an AI partner called Mii who's dressed up as Pikmin. If you can get through an entire level without this partner taking damage, you'll unlock this stamp. This of course easier said than done. Try it on the earliest levels for the best chance of unlocking it.
Capture All Opponents in Basement
In order to capture all of your opponents in the Basement in Luigi's Mansion you need to simply hide at the entrance to the conveyor belts, and then kill them all.
Alternatively you can wait and ride the belt (since you can also float), and then capture your opponents when they appear.
Donkey Kong's Crash Course Strategy
This game has 4 boards to unlock, which is accomplished by beating the previous level. You do that by guiding your cart through the obstacle laden levels to the waiting Donkey Kong. Like the original Donkey Kong game, trial and error, as well as perseverance will be key in learning how to beat each level, and then doing so. One thing to remember is to keep the gamepad as level as possible so the cart doesn't go careening off at high speeds, making it much more difficult to control.
Eyes of the Bulblord (Stamp)
You can achieve this stamp from the boss of mission 4 in the Pikmin Adventure. Instead of attacking the bulbs on the boss's body like you would for the other bosses, instead attack his eyes. If you can destroy his eyes before actually killing him, you'll get this stamp.
First Mastery (Stamp)
Each level in Pikmin Adventure has a mastery stipulation, which can be viewed by beating the level once, and then viewing it in the menu. These stipulations require you to beat the level within a certain time limit, and take no damage while doing so, no easy feat by any means. You'll achieve this stamp if you can master every level.