I'm not for a moment suggesting you carry every single weapon around.

But sometimes it is better to get out those axes you aren't specialised with and bash an assassin than it is to start hacking him up with dagger maladictions when you know full well he runs before he is in danger.

Weapons I'd carry as a warrior, even if not specced, are a couple of axes (limited shield cleave and reduced parrying against assassins and thieves), a staff (for aps, if I was worried about them), and a pair of maces (if I was worried aobut rangers.

I wouldn't carry daggers, flails, whips or swords unless I happened to be specced in them. I'm also not suggesting that you should use a non-specced weapon against everyone you fight. However, if I happened to have landslide, I'd probably use drive against the shaman, or voker, and consider non-specced weapons with it.

Generally though I'm thinking of assassins, rangers, thieves, bards. Classes that can't fully protect from lag and can't soak up damage as well as some other classes.