Team Fortress 2 is slowly turning into an MMO. Since the game's release, they've added unlockable weapons and hats. In the upcoming War Update, they'll introduce item crafting as well.

All the duplicate hats and weapons cluttering your backpack can be used to build stuff that you actually want. "Blueprints—some of which you’ll get right off the bat, others of which you’ll have to puzzle out on your own—will tell you which ingredients you’ll need to combine to make different items," states the TF2 blog.

The War Update should go live within a week or so. Until then, the battle between the Soldier and Demoman classes rages on.