Controller Mods?

[Nick Brocious]

I'm hosting a Super Smash Bros. for Wii U tournament (this is a tournament at my college, fairly casual) and I was wondering how much a modified controller can affect the game. I'll have a Gamecube controller adapter available, so those who want to play with their own Gamecube controller can bring one, but should I have someone check the controller prior to the tournament? Is there a way to gain an unfair advantage?

 

[Mikkelmann]

Turbo controllers can kinda give people an advantage but other then that I think any controller should be fine.