Chibi-Robo - GameCube

Trauma Suit:
Just let Chibi run out of energy, and you'll wake up in your house wearing the trauma suit.

Ghost Suit:
Run out of battery 5 times. The easiest way to do this is by using the Trauma suit's pose by hitting Z.

Drake Redcrest Suit:
Talk to Drake in the living room at night.

Frog suit:
Squirt the frog in the backyard with water. The squirter is under the TV in Jenny's room.

Tao Suit:
Complete the Free Ranger missions.

Super Chibi-Robo Suit:
Activate Giga-Robo.