If you know that your opponent is bringing a gun at high noon, it would be wise to also bring a gun. Some would argue that it would be wise to not show up at all.
However, it would be the height of folly to arrive with a knife. The knife wielder will (usually) be promptly dispatched with a bullet.
"Just like a wop to bring a knife to a gunfight." -Sean Connery in "The Untouchables"