There's a lot of places to pre-order black ops from, but these two places give exclusive stuff!
Amazon: Pre-ordering Black Ops with Amazon will earn you a limited edition laser cel. For those unfamiliar with the term, a laser cel is an image that is printed on Mylar (or Melinex, as it is called in the UK) rather than paper or another easily damageable material.
The laser cel is only available to the first 100, 000 pre-orders so be sure to get yours in quickly! Consumers who receive the laser cel will also receive an exclusive link to download a desktop wallpaper of the same image.
Gamestop: Opting for pre-ordering through Gamestop merits an exclusive, Black Ops themed outfit for your Avatar. Gamestop has said that this offer will apply to either your Xbox Live or PSN Avatar’s. The Avatar Outfit is similar to the suit worn by the pilot of the SR-71 Blackbird in the Black Ops campaign mission WMD. If you decide to order online, you will receive a code to download your Flight Suit outfit while pre-ordering in-store will get you a pre-order card with instructions and download code. Show off your Black Ops dedication in style!
The only problem I see in this, is it's only for your XBL/PSN avatar :( If they introduced this for online multiplayer, that'd be cool!