Something that is uniquely cool and badass. You can't really describe it or want to say something that makes you look like you're jockin' so you just say "hard shit."
It's like when you step into some soft dogshit. It sucks and stays on your shoes and you look stupid. If you step on some hard shit you luck out and it is good fortune because even though you stepped on shit you are smooth enough to not get any on your shoe and as if nothing can touch you.
"Damn, that fool has a sweet rig."
"Yeah, that's some hard shit right there."