The first reward unlock, which has already been met, is a free copy of the original BioShock. The second unlock is for a number of special Team Fortress 2 items. The final unlock will also include a free copy of XCOM: Enemy Unknown. All pre-orders also receive the Industrial Revolution Pack for free, which includes a bunch of in-game bonuses.
Details of the special TF2 items can be found below.
Vox Diabolus
With this Vox Populi anarchist mask, you can terrify your enemies into thinking you're the Devil Himself, or worse, a protestor. Either way, they're probably going to avoid you at the entrance to the supermarket when you try to get them to sign something.
The Pounding Father
Heavy cannot tell lie. Heavy is first President of United States. Of crushing little baby men.
Blind Justice
Want to command respect from people standing at an indeterminate distance from your immediate right? Bolt on a platinum Pinkerton badge and experience the thrill for yourself!
The Person in the Iron Mask
Turkey? Chicken? Game hens? Your head? This cast iron poultry furnace will smoke anything placed inside it.
The Doe-Boy
Protect the important thoughts in your head -- ones like "liberty" and "freedom" and "democracy" -- with good, honest, hat-shaped American steel. This helmet won't run (until heated to 2500°F)!
The Sydney Straw Boat:
Throw this hat on the ground to express rage, or in the air to express joy! Take a hat-based trip through time to learn how your great grandparents displayed emotions in the days before emoticons!
The Steel Songbird:
It gets pretty quiet in that sniper's nest. Why not treat yourself to the haunting rhythmic symphony of bolts being constantly pooped by this mute, easily terrified incontinent bird?
With this Vox Populi anarchist mask, you can terrify your enemies into thinking you're the Devil Himself, or worse, a protestor. Either way, they're probably going to avoid you at the entrance to the supermarket when you try to get them to sign something.
The Pounding Father
Heavy cannot tell lie. Heavy is first President of United States. Of crushing little baby men.
Blind Justice
Want to command respect from people standing at an indeterminate distance from your immediate right? Bolt on a platinum Pinkerton badge and experience the thrill for yourself!
The Person in the Iron Mask
Turkey? Chicken? Game hens? Your head? This cast iron poultry furnace will smoke anything placed inside it.
The Doe-Boy
Protect the important thoughts in your head -- ones like "liberty" and "freedom" and "democracy" -- with good, honest, hat-shaped American steel. This helmet won't run (until heated to 2500°F)!
The Sydney Straw Boat:
Throw this hat on the ground to express rage, or in the air to express joy! Take a hat-based trip through time to learn how your great grandparents displayed emotions in the days before emoticons!
The Steel Songbird:
It gets pretty quiet in that sniper's nest. Why not treat yourself to the haunting rhythmic symphony of bolts being constantly pooped by this mute, easily terrified incontinent bird?
These unlocks are based off of the total number of pre-orders people make for the game. The more pre-orders that come in, the more unlocks there are. You can pre-order BioShock Infinite on Steam for $59.99. There is still over a month remaining, so chances are pretty good all three unlocks will be met.