Extra Levels

Finishing all levels on medium and hard difficulty gives you access to two hidden levels: Aztec and Egyptian.

Natalya

Natalya has an annoying tendency to stand right in your line of fire during a gun battle. If you can, leave her behind while you clear out the area of enemy soldiers. Then go back and get her.

Xenia Onatop

Chuck some mines onto the bridge in the Cuban jungle. Killing Xenia Onatop will be much easier this way as opposed to trying to gun her down.