Press ~ during game play, then enter one of the followings at the console window to activate the corresponding cheat function.

Effect - Code

Toggle invisibility - invisible < 0 or 1>
Spawn Mauser - gimme mauser
Spawn MP40 - gimme mp40
Spawn EP26 - gimme ep26
Spawn MP18 - gimme mp18
Spawn Torba - gimme torba
Spawn PZB39 - gimme pzb39
Spawn Panzerfaust - gimme panzerfaust
Spawn FG4 - gimme fg42