Get Uzi:
Acquire rank 4 in the online demo.

Get USAS-12:
View your multiplayer stats online.

Get F2000:
Play in the Battlefield Veterans program.

Get M60:
Sign up for the Battlefield: Bad Company newsletter.
Conserve Grenades:
Use your knife to bust out the house doors or windows; this will save you grenades.

Get Kits:
Get Recon Kit (QBU88) - your3mynextt4rget
Get Special Ops Kit (UZI) - cov3r1ngthecorn3r
Get Support Kit (M60) - try4ndrunf0rcov3r

More Power Tool Uses:
The Power Tool can be used to break down walls and kill enemies.

Get More Kits:
Get USAS12 Shotgun - Input aw3somef1rep0wer
Get FN2000 - Input h4h4th3r1snoc0d3