Written "nao" or "na0" for geekier persons.
It means "now" in a more bashful and impatient way.
Used a lot in forums or discusion/image boards like "chans" or gamefaqs.
1)
Picz na0 or it didn't happen!!1!
2)
John: I'm hungry
Mom: It will be ready in......
John: NAOOOO!