Press TILDE (~) to enter console mode, and then type in these codes:

heal 1 - Get health for yourself.
happyammo 1 - Turn unlimited ammo on.
happyammo 0 - Turn unlimited ammo off.
kill - Die instantly.
giveitem (ITEM) - Get an item (replace ITEM with a keyword below):

AQUALUNG
ARISAKA
ARISAKAOPT
BACKPACKGB1
BACKPACKGB2
BACKPACKGB3
BACKPACKG ER
BACKPACKRUS
BAR
BAZOOKA
BINOCULARS
BRENGUN
CAMERA
CARBINE
CLUMMYBOMB
COLT
DEG TYAREV
DELISLE
DYNAMITE
ENFIELD
EXPLOSIVESBAG
GARAND
GRENADE36
GRENADE69
GRENADEGE R
GRENADEJAP
K98
K98OPT
KNIFEGER
KNIFESAS
LEE
LEEOPT
MAGNETICMINE
MEDIKIT
MEDIKI TBIG
MINE
MOSIN
MP40
MP44
PANZERFAUST
PARABELLUM
PPS
SHOTGUN
SPAGIN
SPRINGFIELD

SPRINGFIELDOPT
STENGUN
STENGUNSIL
TAISHO
TANKMINE
THOMPSON
TOKAREV
WIRECUTTER
ZB2 6