There are references in Livy's The War with Hannibal that Gallic swords were incredibly soft and tended to bend in battle after a short time. Is there archaeological evidence to support this? If this is true it would make me wonder about the overall lethality of such a weapon since it would be rendered inneffective after the first few minutes of combat.

As for the "swan dive" or the "salmon hop" or whatever it's called in this youtube clip, I have my doubts that it was a specific tactic, but there are references everywhere of Gallic warriors having no fear, throwing themselves into phalanxes and breaking them -- hoplite not sarissa -- and generally fighting like insane people. I mean they did fight naked, so a Gaul throwing himself over the first rank of troops to certain death is something I can imagine them doing. I think the biggest reason the Gallic warrior culture was defeated, was by tactical reform. For example, the Romans were beaten by the Gauls, then they changed their tactics to defeat them. As far as I know the Gauls pretty much stuck with the same tactics win or lose, or am I wrong?