Referencing the use of the FN FAL Rifle - Fusil Automatique Léger (Light Automatic Rifle). To 'FAL' someone implies a kill with the gun on Call of Duty : Modern Warfare 2, which is renowned for its difficultly to use due to its single shot mechanism. Getting a kill or many kills with this gun requires a high degree of accuracy and skill.
However as the meaning of this urban term has evolved, it has grown to mean getting the better of someone when the odds are stacked against you, or perhaps just generally getting the better of someone, often much to their embarrassment.
It has been commented by many that saying this word with a Kentish accent (UK), adds to the effect, as it makes it sound more like the word Fowl.
I just FAL'd him in the face...
Sit there quietly for a prolonged period - then subtly proclaim - 'FAL'd'.OMG
I just FAL'd all over him.
Chard: I took a girl out for dinner last night.
Raskijat: Oh really? What happened next?
Chard: I took her into the bedroom and FAL'd all over her.