Narf

Takes the place of 'psych' or 'not' at the end of a sentence. Meaning the prior statement is illegitimate or false.
Antonym- Nerf
Definition of Nerf:
Reassuring you that a prior statement is truthful.

Narf:

"I'm not a bad ass... NARF!" Meaning i am a bad ass.
"I have a small wiener... NARF" Meaning it's huge.

Nerf:

Brett Curran knows what Nerf really means... Nerf