how do you activate devmode in crysis 2?

Answer 1

right click your crysis exe file then select properties then add -devmode here

then use:

F4 = godmode
F3 = fly/noclip cycle
Numpad 1 = all weapons
Numpad 2 = all ammo

can also use in console:

g_godemode 1
i_unlimitedammo 1
i_giveallitems
i_giveitem <item> eg. i_giveitem LAW
i_noweaponlimit

Answer 2

Add this to your exe patch -devmode