Trainer Options: 1) Unlimited Health: you'll have unlimited health. Although you'll not see the health gauge full, you'll be in critical mass mode. 2) Unlimited Evolution Points: you'll have unlimited EP. 3) One Hit Kills: the name says it all. You should turn this option off when you're playing a protect mission.(if a tank is not instantly destroyed, just charge you're attack and attack it, that should destroy it).
Note: sorry for a bug in One Hit Kills; if you're in tank or a helicopter, it will be destroyed after one hit, but you'll stay alive, so just use this option for normal walking.