So there's a classic Quake style rocket launcher for the Soldier (complete with old-school sound effects and player view model)
Both Engineer and Spy got updates for their weapons if you buy the new Deus Ex game before Aug 22nd
Don't know what the new damage functions are but I do know that the Engineer's new shotgun uses metal instead of ammo and will add metal to your inventory when you make a successful hit.
The Spy's new gun doesn't get random crits but will load crits for every building destroyed (sort of the opposite of the Southern Hospitality).
All the new weapons are quasi-futuristic to match the Deus Ex theme and have similar death animations as the Cow Mangler 3000.
Oh, there are 4 new crate types which finally give Sniper drops (Bazaar Bargain, "strange" sniper rifles, etc)
Deus-ex Pre-order items
http://www.teamfortress.com/deus-ex/
Quake Rocket Launcher
http://www.teamfortress.com/post.php?id=5992
All about the Game tie ins now
TF2 Dota 2 Hats Revealed
http://www.neutralcreeps.com/2011/08/dota-2-hats-for-team-fortress-2.html
I've heard through the grape vine that either a slew of new maps is coming soon or a new game mode...
But yeah, clearly the tie-ins are popular!