For the record, a lot of what the other poster said holds true for the gyms I listed, kind of.
As a BB'er, here's some things that are appealing to me:
Multiple Benches with different angles
Multiple Power racks
Hammer Strength machines (more variety = better, but expensive)
Conventional cardio stuff (Plenty, no one likes waiting to do cardio, haha.)
"Alternative" cardio equipment as well ---> Tires, sleds, prowlers
Some other good things for other types of athletes,
Olympic Platform + Bumper plates
PL-oriented things... cambered bars, reverse GHR machines
As far as a hardcore vibe goes, that's a tricky situation and ultimately your call. It seems like if you're opening up a gym in a less-populous area you're probably going to want to make it a little more marketable towards the masses (though not discouraging good work ethic and "hardcore" attitudes, as you'd have it.)
But if you're in like LA, Miami, NY or something like that... make that shit as dungeon-y and primal as possible. If you build it, they will come.