Signed: George Jefferson. 
Obligatory Mike Birbiglia link: Cracka - YouTube
No hard R? You mean ‘Cacker’?
The thing I’m having a hard time grasping is why a white person would want to call another white person “cracka”.
The white person doing it is wearing a FUBU shirt.
Pass the Sun Chips, cracka.
Sometimes it’s done accidentally, if you verbally include a comma:
Correct: “Pass a saltine cracker”
Horribly offensive: “Pass a saltine <beat> cracker”
I believe the preferred term is Redneck.
In British slang “you’re crackers” (an adjective) means you’re barmy, you’re nuts, you’ve got a screw loose.
“That’s a cracker” means that’s a very good [something].
What the heck does “barmy” mean? If I didn’t know better, I would say you just made that up.
crackers
Riemann: “crackers” Thanks for clearing that up. It all makes sense now.
I guess I’m the only one who has heard of white people calling themselves “crackers”?
White folks who are native to Florida, specifically, tend to use this term in reference to themselves. Florida cracker - Wikipedia
Just to be a pedant: Black people do not just use “nigga” in reference to themselves. For those who use it, it’s often used like “bloke” or “guy” or “folks” is in other English dialects. Like how the Smurfs use “smurf” as a general verb, “nigga” is a general noun. “That nigga Trump is fucking up this country. Niggas are dying over here because of him.” In this sentence, “nigga” does not mean black person or even black people. It means whatever you want it to mean.
I’ve noticed recently (in Reddit videos and such, I wouldn’t be exposed to it otherwise) that some non-black youths now use it too as part of their vernacular, in just the way you describe. So far as I can discern there’s no racist intent, and when non-black youths use it in the company of black youths it seems to be accepted as normal, nobody gets upset. Is that impression correct?
I’m not a black youth, but there is such a thing as a “nigga pass” among young(er) people. You can say “nigga” around your black friend if they are OK with you saying it. But I don’t know anyone older than, say, 40, who follows this “rule”. Most black people my age who say “nigga” have a negative reaction when white people use it, no matter how close a friend the white person may be. It’s a generational thing, I suppose.
There’s the crazy thing the kids these days are all calling “Google”: british slang barmy - Google Search