The Thrustmaster wireless Gamecube and Wii controller is remarkable. Its basically your traditional Gamecube controller but its made in the shape of a PlayStation controller, which may take some getting used to. It works on AAA batteries and has an on/off switch so you can conserve them. Its also got a built in rumble feature.Its pretty small but has a good design so you don't lose grip. The competitor brand, which is the official Nintendo Wavebird wireless controller is around $40 while this Thrustmaster controller is only $25.
I've had it for several months now without any problems whatsoever. The battery life is great also. No lag or poor button response. Everything is instant just like a wired controller.
All systems these days have wireless controllers. Wires are annoying - they get tangled and people trip over them which can lead to the system falling and breaking. Wireless controllers are a great investment and your kids don't need to sit too close to the TV anymore because its got great response from far away.
So if you're looking for a remarkable bargain for a GC/Wii wireless controller, look no further than the Thrustmaster T-Wireless Gamepad For Nintendo Wii And GameCube!
Update On Aug 02, 2009: Oh yeah, forgot to mention.. since its modeled in the shape of a PS2, they give you 4 shoulder buttons instead of just L, R and Z. The 4th button is just an extra Z. Guess they put it there just to polish off the design and make it all look even.
Update On Aug 18, 2009: It has a better feel than the classic Wii controller and since they're the same price you're better off going for this one. The controller is also compatible with virtual console games which are the ones you can download from Wii through WiFi such as Nintendo 64 titles like Zelda: Ocarina of Time or Mario 64.