In game open th consol by pressing ~ type in any of the following cheats

CHEAT - EFFECT
mpcheat ghost - fly
mpcheat walk - stop flying
mpcheat medic - medic capabilities
mpcheat binoculars - aquire binoculars
mpcheat nvg - night vision goggles
mpcheat changeclass * - get waepon

replace * with one of the following weapon codes

spr
mos
v
m9
at4
rpg
m4a1auto