press ~ (the button thats on top of "Tab" on your keyboard" then in the console write in "con_restricted 0" then wrtie "i_unlimitedammo = 1" or "g_infiniteAmmo = 1"
source: http://www.gameshampoo.com/cheatscodes/crysis2cheats.php
Also you can try this
http://www.gamesreviews2010.com/crysis-2-v1-1-1-5620-4-trainer/