EmuNations

It's basically a fork of the Dolphin emulator providing support for legacy devices and other features such as reducing CPU usage on the graphic's thread.The focus seems to be more speed and less on accuracy. 

Please read extensive features via Forum page (GC/Wii section). That said, unless you're feeling quite adventurous or have very old hardware (i.e. D3D9), try the regular Dolphin first. Some people have reported this version works better for them, but it's not a general consensus.