WarioWare for the Gameboy was a breakthrough game combining insane graphic design, simple gameplay, and frenetic pacing to make a fun game. The follow-on WarioWare: Twisted is just as great.
The novelty in Twisted is a motion sensor in the cart. To make things happen in the game you spin your Gameboy around. It's true that this basically turns your Gameboy into an Atari 2600 paddle, but it really works. The rumble pack's tactile feedback adds a lot, little clicks and thumps that let you feel your turning. My favourite minigame so far is a balance game where you tilt the Gameboy to keep the umbrella balanced on the end of your finger.
The game starts with dire warnings to spin only your Gameboy, not yourself, lest you get sick. The warning is so detailed and over the top the first thing I wanted to do was stand up and try spinning myself around.