Hoverbike:


Get a "Great" rank on all Smugglers missions.
Unlimited countermeasures:

Pause the game and press Y, Y, Y, X, X, Z, Z.
Secrets:

Complete the mission below to ubnlock that bonus:
Mission Bonus
2 Super Buggy Boost
3 Special Du Monde
4 Baja Truck
5 Du Monde Oil Slick
7 Baja Truck Bombs
9 Vietnam
10 ATV Monster
11 D-5 Hondo
14 ATV Boost
15 Hondo Oil Slick
18 Sahara Special
20 Sahara Smoke Screen
22 Russian Winter
24 Grenadier
25 Grenadier Bombs
27 Kavostov Halftrack
29 Kavostov Smoke Screen
36 Dual Career Countermeasures