1. Potentially offensive random slur, not necessarily implying one is fucking niggas, like mothafucka may not necessarily imply someone is fucking mothers.
2. Could be both a racial and a homophobic term. For instance, if someone is fuckin' my nigga, they might be a niggafucka. They could also be a faggot. But hell, they could also be your friend's girl too.
3. It could be someone that just goes around fucking people over. If someone's fucking my nigga over, that makes them a niggafucka. Niggafuckin being the act(s) of being a niggafucka that preludes to being a niggafucka.
4. Niggafuckin is a very niggafuckin diverse word that could mean practically whatever the niggafuckin hell you want it to.
"Get cho niggafuckin' ass in the mothafuckin' car."
"Damn, look at this niggafuckin little bitch."
"What, are you niggafuckin me you little shit?!"