Hmm, I don't think "borderline" is misused that often, though. Most ignorant people mislabel it as "bipolar" or "psychotic" or just "crazy". Narcissism is again like depression, where it CAN be used as an adjective that doesn't refer to a pathological disorder.

I think "PTSD" might work, because people use it as an exaggeration. Another good one would be "psychopath" or "sociopath", though people with the disorder probably don't care about its misuse anyway...

Oh, and "retarded". Can't tell you how many times I've heard that.

"Maniac" or "manic" would be good, too, even though that falls under "bipolar".